INSO CORP
424A, 1996-10-08
PREPACKAGED SOFTWARE
Previous: PALLADIAN TRUST, N-30D, 1996-10-08
Next: TALX CORP, S-1/A, 1996-10-08



<PAGE>   1

                                           Filed pursuant to Rule 424(a)
                                           Registration Statement No. 333-12695

     INFORMATION CONTAINED HEREIN IS SUBJECT TO COMPLETION OR AMENDMENT. A
     REGISTRATION STATEMENT RELATING TO THESE SECURITIES HAS BEEN FILED WITH THE
     SECURITIES AND EXCHANGE COMMISSION. THESE SECURITIES MAY NOT BE SOLD NOR
     MAY OFFERS TO BUY BE ACCEPTED PRIOR TO THE TIME THE REGISTRATION STATEMENT
     BECOMES EFFECTIVE. THIS PROSPECTUS SHALL NOT CONSTITUTE AN OFFER TO SELL OR
     THE SOLICITATION OF AN OFFER TO BUY NOR SHALL THERE BE ANY SALE OF THESE
     SECURITIES IN ANY STATE IN WHICH SUCH OFFER, SOLICITATION OR SALE WOULD BE
     UNLAWFUL PRIOR TO REGISTRATION OR QUALIFICATION UNDER THE SECURITIES LAWS
     OF ANY SUCH STATE.
 
                                                           SUBJECT TO COMPLETION
                                                              SEPTEMBER 25, 1996
                                1,200,000 SHARES
                                  [INSO LOGO]
                                  COMMON STOCK
                               ------------------
 
     All of the shares of Common Stock offered hereby are being sold by INSO
Corporation ("INSO" or the "Company"). The Company's Common Stock is traded on
the Nasdaq National Market under the symbol "INSO." On September 24, 1996, the
last reported sale price of the Common Stock on the Nasdaq National Market was
$56.50 per share. See "Price Range of Common Stock and Dividend Policy."
                               ------------------
        THE COMMON STOCK OFFERED HEREBY INVOLVES A HIGH DEGREE OF RISK.
                    SEE "RISK FACTORS" BEGINNING ON PAGE 6.
                               ------------------
THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES AND
  EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION NOR HAS THE
     SECURITIES AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION
      PASSED UPON THE ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY
        REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.
 
<TABLE>
<S>                           <C>                    <C>                    <C>
- -------------------------------------------------------------------------------------------------
- -------------------------------------------------------------------------------------------------
                                      PRICE              UNDERWRITING             PROCEEDS
                                       TO                DISCOUNTS AND               TO
                                     PUBLIC               COMMISSIONS            COMPANY(1)
- -------------------------------------------------------------------------------------------------
  Per Share.................            $                      $                      $
- -------------------------------------------------------------------------------------------------
  Total(2)..................            $                      $                      $
- -------------------------------------------------------------------------------------------------
- -------------------------------------------------------------------------------------------------
</TABLE>
 
(1) Before deducting estimated expenses of $265,000, all of which will be
    payable by the Company.
 
(2) The Company has granted to the Underwriters a 30-day option to purchase up
    to 180,000 additional shares of Common Stock solely to cover
    over-allotments, if any. To the extent the option is exercised, the
    Underwriters will offer the additional shares at the Price to Public. If
    such option is exercised in full, the total Price to Public, Underwriting
    Discounts and Commissions and Proceeds to Company will be $            ,
    $            and $            , respectively. See "Underwriting."
                               ------------------
     The shares of Common Stock are offered by the several Underwriters, subject
to prior sale, when, as and if delivered to and accepted by them, and subject to
the right of the Underwriters to reject any order in whole or in part. It is
expected that delivery of the shares of Common Stock will be made at the offices
of Alex. Brown & Sons Incorporated, Baltimore, Maryland, on or about
            , 1996.
ALEX. BROWN & SONS
           INCORPORATED
                           ADAMS, HARKNESS & HILL, INC.
 
                                                MONTGOMERY SECURITIES
 
               THE DATE OF THIS PROSPECTUS IS             , 1996.
<PAGE>   2
 
     [Graphic on inside front cover of the Prospectus consists of (i) the
Company's logo and address and (ii) the Company's World Wide Web homepage. The
homepage contains a tool bar with the following selections: Purchase, Products,
Corporate, Contact Us and Site Index. The left side of the homepage contains the
selections: Welcome, What's New, International, ebt and About Inso. The
remainder of the homepage contains the Company's logo, address and telephone and
fax numbers and the following text:
 
     INSO Corporation is a leading provider of multilingual software products
     and systems that help people correct, find, view, publish, and distribute
     data, text, and images in electronic environments ranging from individual
     desktops to the Internet. The Company markets certain of its products
     worldwide to OEMs of computer hardware, software, and consumer electronics
     products. The Company also markets software applications and systems to
     major corporations, government agencies, and end users.]
 
                            ------------------------
 
     IN CONNECTION WITH THIS OFFERING, THE UNDERWRITERS MAY OVER-ALLOT OR EFFECT
TRANSACTIONS WHICH STABILIZE OR MAINTAIN THE MARKET PRICE OF THE COMMON STOCK OF
THE COMPANY AT A LEVEL ABOVE THAT WHICH MIGHT OTHERWISE PREVAIL IN THE OPEN
MARKET. SUCH TRANSACTIONS MAY BE EFFECTED ON THE NASDAQ NATIONAL MARKET, OR
OTHERWISE. SUCH STABILIZING, IF COMMENCED, MAY BE DISCONTINUED AT ANY TIME.
 
     IN CONNECTION WITH THIS OFFERING, CERTAIN UNDERWRITERS (AND SELLING GROUP
MEMBERS) OR THEIR RESPECTIVE AFFILIATES MAY ENGAGE IN PASSIVE MARKET MAKING
TRANSACTIONS IN THE COMMON STOCK OF THE COMPANY ON THE NASDAQ NATIONAL MARKET IN
ACCORDANCE WITH RULE 10B-6A UNDER THE SECURITIES EXCHANGE ACT OF 1934. SEE
"UNDERWRITING."
 
                                        2
<PAGE>   3
 
                               PROSPECTUS SUMMARY
 
     The following summary is qualified in its entirety by reference to the more
detailed information and the Consolidated Financial Statements and Notes thereto
appearing elsewhere in this Prospectus as well as the information incorporated
herein by reference. Unless otherwise indicated, all information contained in
this Prospectus assumes that the Underwriters' over-allotment option will not be
exercised. This Prospectus contains forward-looking statements which involve
risks and uncertainties. The Company's actual results could differ materially
from those anticipated in these forward-looking statements as a result of
certain factors, including those set forth under "Risk Factors" and elsewhere in
this Prospectus.
 
                                  THE COMPANY
 
     INSO Corporation ("INSO" or the "Company") is a leading provider of
multilingual software products and systems that help people correct, find, view,
publish, and distribute data, text, and images in electronic environments
ranging from individual desktops to the Internet. The Company markets certain of
its products worldwide to original equipment manufacturers ("OEMs") of computer
hardware, software, and consumer electronics products. The Company also markets
software applications and systems to major corporations, government agencies,
and end users. The Company currently has nearly 450 OEM customers and over 600
direct corporate licensees, and the Company believes that the worldwide
installed base of end-user licensees of OEM products incorporating INSO's
technology exceeds 50,000,000.
 
     The Company's products are divided into four categories:
 
     - Proofing Tools.  The Company's Proofing Tools product line includes
       software programs and related databases for correcting errors in
       spelling, grammar, punctuation, capitalization, spacing, and other
       mistakes in documents created by users of computer applications. The
       Company's Proofing Tools products include OEM products such as
       International CorrectSpell, the industry-standard spelling correction
       system; International ProofReader, a multilingual proofreading system
       available in 10 languages that addresses numerous classes of writing
       errors and style problems; and CorrectText Grammar Correction System, the
       leading English grammar correction technology used in word processors
       today. The Proofing Tools product line also includes the Company's
       CorrectEnglish English-as-a-Second Language writing system products,
       CyberSpell, SciWords, and InWords. Examples of products using the
       Company's Proofing Tools include Word and Office by Microsoft Corporation
       ("Microsoft"), WordPro, SmartSuite, and Notes by Lotus Development
       Corporation, and a version of Powerpack by Netscape Communications
       Corporation.
 
     - Information Management Tools.  The Company's Information Management Tools
       product line includes both search and indexing enhancement products and
       file filtering, viewing, and conversion products. These products include
       IntelliScope, a multilingual tool that performs linguistic analysis; Inso
       Search Wizard, an interactive search expansion and refinement utility;
       the Outside In OEM viewing technology; the Quick View Plus end-user
       product, an application that provides corporations and consumers with the
       ability to view, export, copy, and print files originating in any of over
       200 applications; and the ImageStream graphics filters OEM product, which
       permits the exchange of graphical images among more than 60 charting,
       presentation, and graphical applications. Examples of products using the
       Company's Information Management Tools include Microsoft's Windows 95,
       Fulcrum Technology Inc.'s SearchServer, and Novell, Inc.'s GroupWise.
 
     - Information Products.  The Company's Information Products product line
       includes the Company's electronic reference works, proprietary
       information databases, and software retrieval technology. The Information
       Products line includes more than 60 reference titles, including The
       Columbia Encyclopedia, Fifth Edition, The Concise Columbia Electronic
       Encyclopedia, and the American Heritage dictionaries. The Company's
       Information Products also include reference products developed from its
       proprietary information databases. Certain of these products are
       published in print form as the Information Please almanacs and the A&E
       Entertainment Almanac. The Company anticipates that it will continue to
       add to its proprietary information databases and produce new reference
       products from those databases. Examples of products using the Company's
       Information Products include Microsoft's Bookshelf, CompuServe, Inc.'s
       CompuServe Information Service, Starwave Corporation's ESPNET
 
                                        3
<PAGE>   4
 
       SportsZone, InterGO Communications, Inc.'s InterGO, AT&T New Media
       Services' AT&T Business Network, and Bloomberg L.P.'s THE BLOOMBERG.
 
     - Electronic Publishing Solutions.  The Company's Electronic Publishing
       Solutions are software solutions based on the use of structured
       documents, together with proprietary search and retrieval software, to
       address mission-critical publishing problems on an enterprise level.
       These products include the DynaText publishing system, which is composed
       of automated and interactive tools to create structured content from
       commonly used word processing and page makeup systems, and browsing
       technology that permits users to select from among specific views and
       structures to personalize the retrieval and presentation of data. These
       products allow major corporations and government users to distribute and
       maintain complex documents in many languages through multiple media such
       as print, CD-ROM, LANs, WANs, and the World Wide Web.
 
     The Company's strategy is to concentrate its development and marketing
efforts on building and promoting solutions where the combination of its core
competencies can create substantial added value and to optimize those solutions
for markets and market segments where the Company can achieve a significant
position. Key elements of the Company's strategy include (i) extending its
technological lead in its core competencies, (ii) diversifying its product
offerings and product lines, (iii) diversifying its distribution channels, and
(iv) accelerating its growth and strengthening its core competencies through
acquisitions.
 
     Prior to its initial public offering of Common Stock in March 1994 (the
"IPO"), the Company operated as the Software Division (the "Software Division")
of Houghton Mifflin Company ("Houghton Mifflin"). As of August 31, 1996,
Houghton Mifflin held 4,015,100 shares of Common Stock, representing
approximately 30.7% (28.1% after giving effect to this offering) of the
outstanding shares of Common Stock. Pursuant to the terms of Houghton Mifflin's
6% Exchangeable Notes Due 1999 ("Stock Appreciation Income Linked Securities" or
"SAILS(SM)"), Houghton Mifflin may, at its option, deliver to the SAILS holders
up to 3,840,000 shares of Common Stock of the Company held by Houghton Mifflin
upon exchange of the SAILS. See "Relationship with Houghton Mifflin."
 
                               ACQUISITION OF EBT
 
     On July 16, 1996, the Company acquired all of the outstanding capital stock
of Electronic Book Technologies, Inc., renamed INSO Providence Corporation
("EBT" or "INSO Providence"), a leading developer of electronic publishing tools
and solutions that form the core of the Company's Electronic Publishing
Solutions product category. In connection with the EBT acquisition, the Company
paid $27,800,000 in cash in July 1996 and is obligated to pay an additional
$1,500,000 to the former principal stockholder of EBT in January 1998 and up to
an additional $10,400,000 to purchase shares of EBT stock issuable upon exercise
of outstanding EBT stock options. In the event that certain EBT financial and
operating goals are met, contingent payments of up to an additional $5,300,000
will be paid by the Company. The acquisition was accounted for as a purchase and
included the acquisition of certain technology under research and development,
which will result in a charge of $34,300,000 to the Company's earnings in the
third quarter of 1996.
                            ------------------------
 
     The Company is incorporated in Delaware. The Company's principal executive
offices are located at 31 St. James Avenue, Boston, MA 02116, and its telephone
number is (617) 753-6500.
 
     CorrecText (R), Information Please(R), IntelliFinder (R), IntelliScope(R),
Outside In(R), Quick View Plus (R), ImageStream(R), CADleaf (R), DynaText (R),
DynaTag (R), and DynaWeb (R)are registered trademarks of INSO Corporation or one
of its wholly owned subsidiaries. International CorrectSpell (TM), International
ProofReader (TM), CorrectEnglish (TM), InWords (TM), Inso Search Wizard (TM),
and CyberSpell (TM)are trademarks of INSO Corporation or one of its wholly owned
subsidiaries. Windows (R) 95, Word (R), and Office (R) are registered trademarks
of Microsoft Corporation; WordPro (R), SmartSuite (R), and Notes (R) are
registered trademarks of Lotus Development Corporation; American Heritage (R) is
a registered trademark of Forbes, Inc.; A&E (R) is a registered trademark of the
Arts & Entertainment Network, Inc.; and InterGO (TM) is a trademark of InterGO
Communications, Inc. All other trademarks, service marks or trade names referred
to in this Prospectus are the property of their respective owners.
 
                                        4
<PAGE>   5
 
                                  THE OFFERING
 
<TABLE>
<S>                                                      <C>
Common Stock offered by the Company....................  1,200,000 shares
Common Stock to be outstanding after the offering......  14,284,224 shares(1)
Use of proceeds........................................  General corporate purposes,
                                                         including research and development
                                                         and potential acquisitions.
Nasdaq National Market symbol..........................  INSO
</TABLE>
 
- ---------------
(1) Excludes 3,852,714 shares of Common Stock issuable upon the exercise of
    options outstanding as of September 24, 1996.
 
                   SUMMARY CONSOLIDATED FINANCIAL INFORMATION
                    (IN THOUSANDS, EXCEPT PER SHARE AMOUNTS)
 
<TABLE>
<CAPTION>
                      PRO FORMA
                      SIX MONTHS       SIX MONTHS           PRO FORMA              YEAR ENDED
                        ENDED        ENDED JUNE 30,         YEAR ENDED            DECEMBER 31,
                       JUNE 30,    -------------------     DECEMBER 31,   -----------------------------
                       1996(1)      1996        1995         1995(1)       1995        1994      1993
                      ----------   -------     -------     ------------   -------     -------   -------
<S>                   <C>          <C>         <C>         <C>            <C>         <C>       <C>
STATEMENT OF
  OPERATIONS DATA:
Net revenues.........  $ 35,093    $27,605     $17,925       $ 57,201     $43,387     $23,463   $13,757
Operating income.....     3,493      5,201         883         11,089      11,578       8,533     4,386
Net income (loss)....     1,296(2)   2,720(2)   (1,363)(3)      5,479       5,994(3)    5,663     2,575
Primary net income
  (loss) per share...  $   0.09(2) $  0.20(2)  $ (0.11)(3)   $   0.45     $  0.49(3)  $  0.48   $  0.22(4)
Weighted average
  shares
  outstanding........    13,690     13,690      12,292         12,228      12,228      11,798    11,560(4)
</TABLE>
 
<TABLE>
<CAPTION>
                                                                             JUNE 30, 1996
                                                                ---------------------------------------
                                                                                           PRO FORMA
                                                                ACTUAL    PRO FORMA(1)   AS ADJUSTED(5)
                                                                -------   ------------   --------------
<S>                                                             <C>       <C>            <C>
BALANCE SHEET DATA:
Working capital...............................................  $57,538     $ 19,961        $ 84,106
Total assets..................................................   91,729       68,564         132,709
Stockholders' equity..........................................   80,464       46,164         110,309
</TABLE>
 
- ---------------
(1) The pro forma consolidated statement of operations data for the six months
    ended June 30, 1996 and the year ended December 31, 1995 give pro forma
    effect to the Company's July 16, 1996 acquisition of EBT (including payments
    by the Company for the EBT stock issuable upon exercise of outstanding EBT
    stock options) as if such acquisition had occurred on January 1, 1996 and
    1995, respectively, and the pro forma consolidated balance sheet data at
    June 30, 1996 give pro forma effect to the EBT acquisition as if it had
    occurred on June 30, 1996. The pro forma statement of operations data for
    the six months ended June 30, 1996 and the year ended December 31, 1995 do
    not reflect a charge of $34,300,000 for certain purchased in-process
    research and development to be recorded by the Company in the third quarter
    of 1996. See the Company's Pro Forma Consolidated Financial Information
    (Unaudited) appearing elsewhere herein.
 
(2) Acquisition-related charges for certain purchased technology under research
    and development at Imagemark Software Labs, Inc. (renamed INSO Kansas City
    Corporation), which was acquired by the Company in January 1996, reduced net
    income and net income per share for the six months ended June 30, 1996
    (actual and pro forma) by $4,400,000 and $0.32, respectively. See
    "Management's Discussion and Analysis of Financial Condition and Results of
    Operations."
 
(3) Acquisition-related charges for certain purchased technology under research
    and development at Systems Compatibility Corporation (renamed INSO Chicago
    Corporation), which was acquired by the Company in April 1995, reduced net
    income and net income per share for the six months ended June 30, 1995 and
    the year ended December 31, 1995 by $5,500,000 and $0.45, respectively. See
    "Management's Discussion and Analysis of Financial Condition and Results of
    Operations."
 
(4) Assumes that the 11,560,000 shares of Common Stock outstanding immediately
    after the Company's initial public offering were outstanding throughout
    1993.
 
(5) Adjusted to give effect to the sale by the Company of 1,200,000 shares of
    Common Stock offered hereby at an assumed public offering price of $56.50
    per share (the last reported sale price on the Nasdaq National Market on
    September 24, 1996) and after deducting estimated underwriting discounts and
    commissions and offering expenses and the application of the net proceeds
    therefrom. See "Use of Proceeds" and "Capitalization."
 
                                        5
<PAGE>   6
 
                                  RISK FACTORS
 
     In addition to the other information in this Prospectus (including all
documents incorporated by reference herein), the following factors should be
considered carefully in evaluating an investment in the Common Stock offered by
this Prospectus. This Prospectus contains forward-looking statements which
involve risks and uncertainties. The Company's actual results could differ
materially from the results anticipated in these forward-looking statements as a
result of certain of the factors set forth in the following risk factors and
elsewhere in this Prospectus.
 
     Reliance on Key Customers.  For the year ended December 31, 1995, five of
the Company's customers accounted for 67% (64%, if certain non-recurring revenue
earned from royalty audits is excluded) of its revenues, compared to 69% for the
year ended December 31, 1994. Microsoft accounted for 52% (50%, if certain
non-recurring revenue earned from royalty audits is excluded) of the Company's
revenues for the year ended December 31, 1995, compared to 55% for the year
ended December 31, 1994. The Company anticipates that the percentage of its
revenue from Microsoft will decline further as the Company continues to expand
its product offerings and diversify its customer base. A loss of, or significant
decline in, revenues from any key customer could have a material adverse effect
on the Company's business, financial condition, and results of operations.
 
     Most of the revenues received by INSO from Microsoft derive from the use of
INSO's Proofing Tools in Microsoft's Word and Office products. During 1995, the
Company amended its agreement with Microsoft with respect to Proofing Tools.
Under the terms of the amended agreement, the Company has granted to Microsoft,
for substantially equal fixed quarterly minimum payments in 1996 and 1997, (i) a
license to use version 3.02 of INSO's grammar product (the "Licensed Grammar
Product") in specified versions of Microsoft's Word and Office products and (ii)
an unlimited license to use a version of INSO's spelling and thesaurus products
in all Microsoft products. Depending on the versions of Word and Office in which
Microsoft uses the Licensed Grammar Product after June 30, 1996, INSO can earn
additional predetermined revenues ("Usage Fees") through the termination date of
the agreement (March 2001). INSO expects that its revenues for the third quarter
of 1996 will include certain such Usage Fees. There can be no assurance,
however, that INSO will receive any revenues from Microsoft after December 1997
with respect to the Licensed Grammar Product. It is also possible that
Microsoft, in the future, could add features and functionality to its operating
systems, including future versions of Windows 95 and Windows NT, that may
compete with the Company's products and reduce demand for the Company's products
by Microsoft or the Company's other OEM customers. Any such development could
reduce the Company's revenues from Microsoft and have a material adverse effect
on the Company's business, financial condition, and results of operations. See
"Business -- Key Customers."
 
     Dependence on OEMs.  The Company receives the majority of its revenues from
OEMs that integrate the Company's products with their own products and market
them to end users as a single unit. The business of the Company's OEM customers
is intensely competitive, and the computer software industry has continued to
consolidate. As a result, there is both a decreasing number of potentially
significant OEM customers for the Company's products and increasing competitive
pressure for the Company's existing and potential customers to reduce costs. At
the same time, it is possible that consumers may reduce purchases of the
products of OEMs for reasons unrelated to the quality or price of the Company's
products. It is also possible that consolidation within the software industry
will reduce the need for competitors to differentiate their products based on
features such as those provided by the Company's OEM products, which could in
turn reduce the demand for the Company's products from OEM customers. These
factors could result in decreased revenues from OEMs, as well as the loss of
significant OEM customers, such as Microsoft, who may choose to develop products
internally that compete with those of the Company in order to reduce their
costs. In addition, economic conditions, inventory positions, the ability to
sell the Company's products to end users, and other marketing restrictions that
adversely affect the operations of the Company's OEMs could have a substantial
impact upon the Company's financial results. No assurances can be
 
                                        6
<PAGE>   7
 
given that the Company's OEMs will not experience financial or other
difficulties that could adversely affect their operations, and, in turn, the
operating results of the Company.
 
     New Marketing Approaches.  To reduce its reliance on OEMs, the Company is
marketing certain of its products through direct sales efforts aimed at major
corporations and government agencies, traditional software distribution
channels, and electronic distribution. The Company intends to expand this
activity through greater sales efforts and the introduction of new products for
corporate and government use. The success or failure of these efforts will have
a substantial impact on the Company's ability to sustain its historical rates of
revenue and net income growth. In addition, the marketing and distribution of
products directly to end users, either by the Company or by resellers or
distributors, requires higher sales and marketing expenditures as a percentage
of revenues than the OEM distribution channel, which could have a negative
impact on the Company's operating results. Products distributed through
electronic means have not historically contributed significantly to the
Company's revenues or operating results, and there may be either consumer
dissatisfaction with the Company's products or a reluctance on the part of
consumers to receive or purchase products through such means. If the Company is
unable to achieve substantial revenues from direct electronic distribution, the
marketing of products to end users through more traditional reseller and
distribution channels could result in both lower revenues and lower operating
margins on those revenues.
 
     Integration of EBT.  On July 16, 1996, the Company acquired all of the
outstanding capital stock of EBT. EBT is substantially larger, in terms of
number of employees and revenues, than the businesses that INSO has previously
acquired. EBT has historically marketed its products almost exclusively through
direct and reseller distribution channels. There can be no assurance that the
operations of EBT can be successfully integrated with those of the Company. In
addition, certain of the technologies currently under development at EBT are not
complete and have not gained market acceptance, and the Company is unable to
predict the level of additional research and development expenditures that may
be required to make those technologies competitive in their intended markets.
The Company anticipates that those technologies could require substantial
ongoing research and development expenditures in order to expand their markets.
 
     Competition and Market Trends.  The computer software market is highly
competitive. Some of the Company's competitors or potential competitors have
substantially greater development, marketing, sales, and financial resources
than the Company. The Company has historically operated in market segments that
have attracted fewer substantial participants than the general market for
software applications. With the development of products for end users,
particularly in the Information Management Tools market and as a result of the
acquisition of EBT, the Company has begun to participate in broader markets
where it anticipates increased competition, both as to quality and price, from
entities with greater resources than those of the Company, including existing
participants in those markets. These competitors or potential competitors may be
able to adapt more quickly to new or emerging technologies and standards or
changes in customer requirements or may be able to devote greater resources to
the promotion and sale of their products than the Company. It is also possible
that competitors or potential competitors may have more ability than the Company
to control pricing and marketing decisions affecting their revenues. Continued
investment in research and development and in marketing efforts will be required
to permit the Company to compete successfully in this industry, and there is no
assurance that the Company will have the necessary capital to fund that
investment.
 
     New Products and Technological Change.  The Company's future performance
will depend upon its ability to enhance its current products, successfully
complete products currently under research and development, introduce new
products that keep pace with technological developments, respond to changing
customer requirements, and achieve market acceptance. Any failure by the Company
to anticipate or respond adequately to technological developments and customer
requirements, or any significant delay in product development or introduction,
could have a material adverse effect upon the Company. In addition, undetected
errors and performance deficiencies
 
                                        7
<PAGE>   8
 
which are not corrected prior to product releases may require the Company to
expend additional resources to prepare remedies or redesign products, and may
result in reduced customer goodwill. Delays or difficulties in the distribution
or marketing, or lack of market acceptance, of new products could have a
material adverse effect on the Company's business, financial condition, and
results of operations in the future.
 
     Future Acquisitions of Businesses and Assets.  The Company's historical and
projected growth has come from a combination of growth from internally developed
products and the successful acquisition and integration of businesses and
assets. Changes in the availability of acquisition candidates on attractive
terms could make it more difficult for the Company to achieve growth levels
consistent with those historically achieved. In addition, the Company's ability
to achieve growth in revenues and net income from the development of new
Information Products is dependent to a large degree on the Company's ability to
acquire, either by license or purchase, the rights to additional authoritative
reference works. Changes in the market for the electronic rights to such works
could make it difficult or impossible for the Company to acquire such rights on
favorable economic terms, which could materially adversely affect the Company's
revenues and operating results.
 
     Dependence on Key Personnel.  The Company's ability to remain competitive
in the software industry is dependent on the services of a number of key
technical personnel, principally software engineers, linguists, and database
specialists. Competition for such personnel in the software industry is intense.
None of the Company's officers or key employees is bound by employment
agreements. In addition, personnel costs for technical staff represent a
significant portion of the Company's operating expenses, and increased
competition and related personnel cost increases for such staff could have a
material adverse impact on the Company's business, financial condition, and
results of operations.
 
     International Operations.  The Company has recently commenced actively
marketing its products to end users outside the United States and, with the
acquisition of EBT, it is currently anticipated that the percentage of the
Company's total revenues that is derived from sales to end users in foreign
markets will likely increase. The marketing of products to end users outside the
United States, directly or through resellers and distributors, increases the
risk to the Company's revenues associated with fluctuations of the U.S. dollar
in relation to foreign currencies. Such fluctuations could also result in
increased operating expenses associated with foreign operations. In addition,
the development of end-user products for overseas markets requires additional
investments in product development. The Company does not have substantial
expertise in the development of end-user products for such markets, and there is
the possibility that increased development expenditures for such products will
have an adverse impact on the Company's business, financial condition, and
results of operations.
 
     Additional risks inherent in the Company's international business
activities generally include unexpected changes in regulatory requirements,
tariffs, and other trade barriers, longer accounts receivable payment cycles,
potentially adverse tax consequences, potentially less comprehensive
intellectual property protection, and the burdens of complying with a wide
variety of foreign laws. There can be no assurance that such factors will not
have an adverse effect on the Company's future international revenues and,
consequently, the Company's business, financial condition, and results of
operations.
 
     Dependence on Content Suppliers.  Several of the Company's major
Information Products, including the American Heritage electronic dictionaries
and Roget's II Electronic Thesaurus, incorporate database content from Houghton
Mifflin which is subject to a written license agreement expiring December 31,
1998, except that customer licenses in effect on the termination date will
remain in effect. Any extension of that license agreement or any future proposal
for use of Houghton Mifflin database content in the Company's products will be
based on arm's-length negotiations with Houghton Mifflin. There can be no
assurance that the Company will be able to continue to market
 
                                        8
<PAGE>   9
 
and develop such products if its existing license were to terminate. See
"Business--Third-Party Database and Content Supply Arrangements."
 
     Fluctuations in Quarterly Operating Results.  The Company operates without
substantial backlog and quarterly revenues are difficult to forecast, and may
fluctuate as a result of a number of factors, including without limitation the
timing of new product introductions; announcements of new products by the
Company, its competitors, or its customers; delays in customer purchases in
anticipation of industry developments; and gross profit margin variations
relating to variations in product mix involving products with different royalty
rates payable to database suppliers. As a result, the Company believes that
period-to-period comparisons of its operating results are not necessarily
meaningful and should not be relied upon as indications of future performance.
In addition, it is likely that in some future quarter the Company's operating
results will be below the expectations of public market analysts and investors.
In such event, the price of the Company's Common Stock would likely be
materially adversely affected.
 
     Concentration of Ownership.  Immediately following the issuance and sale of
1,200,000 shares of Common Stock being offered hereby by the Company, Houghton
Mifflin will hold 4,015,100 shares of Common Stock or 28.1% of the Company's
outstanding Common Stock. Of such shares, Houghton Mifflin exercises voting
rights with respect to all shares issuable upon conversion of the SAILS (up to
3,840,000 shares) until such time or times, if any, as the SAILS are exchanged
or redeemed for shares of Common Stock. Accordingly, Houghton Mifflin will
continue to have the ability to influence significantly the election of all of
the Company's directors and most corporate actions. The Company has agreed, so
long as Houghton Mifflin owns at least 20% of the outstanding Common Stock of
the Company, to nominate two persons designated by Houghton Mifflin to serve on
its Board of Directors. Currently, Houghton Mifflin has designated only one such
director. Such a level of ownership also may have the effect of delaying,
deferring, or preventing a change in the control of the Company. Sales of Common
Stock by Houghton Mifflin pursuant to Rule 144 under the Securities Act of 1933,
as amended (the "Securities Act"), or other exemptions from registration, or
pursuant to registration rights, may have an adverse effect on the market price
for the Common Stock and could impair the Company's ability to raise capital
through an offering of its equity securities. See "Relationship with Houghton
Mifflin."
 
                                USE OF PROCEEDS
 
     The net proceeds to the Company from the sale of the 1,200,000 shares of
Common Stock offered by the Company hereby are estimated to be $64,145,000
($73,806,500 if the Underwriters' over-allotment option is exercised in full)
after deducting estimated underwriting discounts and commissions and offering
expenses payable by the Company and assuming a public offering price of $56.50
per share (the last reported sale price on September 24, 1996).
 
     The Company intends to use the net proceeds for general corporate purposes,
including (i) research and development efforts to enhance the Company's existing
software products and to develop new products; (ii) acquisitions of information
content and technologies; and (iii) acquisitions of businesses that are
potentially complementary to the Company's business. Pending such uses, the net
proceeds of this offering will be invested in investment grade, interest-bearing
securities. The Company currently has no commitments or agreements for the
acquisition of any businesses.
 
                                        9
<PAGE>   10
 
                          PRICE RANGE OF COMMON STOCK
                              AND DIVIDEND POLICY
 
     The Common Stock of the Company is listed on the Nasdaq National Market
under the symbol "INSO." The following table sets forth the high and low sales
prices per share of the Company's Common Stock for the calendar periods listed
below as reported on the Nasdaq National Market. Such information reflects
interdealer prices, without retail markup, markdown, or commission, and may not
represent actual transactions.
 
<TABLE>
<CAPTION>
                                                                          HIGH         LOW
                                                                         ------       ------
<S>                                                                      <C>          <C>
1994
     First Quarter (from March 1, 1994)................................  $12.25       $ 8.57
     Second Quarter....................................................   12.88         8.63
     Third Quarter.....................................................   14.50        10.50
     Fourth Quarter....................................................   17.88        13.75
1995
     First Quarter.....................................................  $25.88       $16.53
     Second Quarter....................................................   32.50        24.13
     Third Quarter.....................................................   36.25        29.38
     Fourth Quarter....................................................   47.50        27.25
1996
     First Quarter.....................................................  $50.25       $31.25
     Second Quarter....................................................   68.00        45.75
     Third Quarter (through September 24, 1996)........................   58.50        39.25
</TABLE>
 
     On September 1, 1995, the Company effected a two-for-one stock split in the
form of a stock dividend of one share of Common Stock for each outstanding share
of Common Stock. The dividend was payable to stockholders of record on August
18, 1995. All references in the above table have been retroactively restated to
reflect this transaction.
 
     On September 24, 1996, the last reported sale price of the Common Stock on
the Nasdaq National Market was $56.50 per share. As of September 24, 1996, the
Company's Common Stock was held by 454 holders of record. The number of record
holders may not be representative of the number of beneficial holders because
many shares are held by depositaries, brokers, or other nominees. The Company
has paid no cash dividends on its Common Stock since its formation and has no
present plans to do so.
 
                                       10
<PAGE>   11
 
                                 CAPITALIZATION
 
     The following table sets forth as of June 30, 1996 (i) the actual
capitalization of the Company, (ii) the pro forma capitalization of the Company
as described in Note (1) below, and (iii) the pro forma capitalization of the
Company as adjusted to reflect the issuance and sale by the Company of 1,200,000
shares of Common Stock offered hereby at an assumed public offering price of
$56.50 per share (the last sale price on September 24, 1996) and receipt of the
net proceeds therefrom, after deducting estimated underwriting discounts and
commissions and offering expenses payable by the Company. This table should be
read in conjunction with the consolidated financial statements of the Company
and the related notes thereto appearing elsewhere in this Prospectus. See
"Selected Consolidated Financial Information" and "Management's Discussion and
Analysis of Financial Condition and Results of Operations."
 
<TABLE>
<CAPTION>
                                                                      JUNE 30, 1996
                                                          --------------------------------------
                                                                                      PRO FORMA
                                                          ACTUAL    PRO FORMA(1)     AS ADJUSTED
                                                          -------   ------------     -----------
                                                          (IN THOUSANDS)
<S>                                                       <C>       <C>              <C>
Stockholders' equity:
Preferred stock, $.01 par value; 1,000,000 shares
  authorized; none issued...............................       --           --               --
Common stock, $.01 par value; 50,000,000 shares
  authorized; 13,078,448 shares issued (actual and pro
  forma) and 14,278,448 shares issued (pro forma as
  adjusted)(2)..........................................  $   131     $    131        $     143
Capital in excess of par value..........................   66,585       66,585          130,718
Retained earnings.......................................   14,377      (19,923)         (19,923)
                                                          -------     --------        ---------
                                                          $81,093     $ 46,793        $ 110,938
Unamortized value of restricted shares..................     (572)        (572)            (572)
Treasury stock, at cost, 5,075 shares...................      (57)         (57)             (57)
                                                          -------     --------        ---------
          Total stockholders' equity....................  $80,464     $ 46,164        $ 110,309
                                                          =======     ========        =========
</TABLE>
 
- ---------------
(1) Gives pro forma effect to the July 16, 1996 acquisition of EBT (including
    payments by the Company for the EBT stock issuable upon exercise of
    outstanding EBT stock options) by the Company as if such acquisition had
    occurred on June 30, 1996.
 
(2) Excludes 2,294,114 shares of Common Stock issuable upon the exercise of
    options outstanding as of June 30, 1996.
 
                                       11
<PAGE>   12
 
                  SELECTED CONSOLIDATED FINANCIAL INFORMATION
 
     The following selected financial information for the three years ended
December 31, 1995, have been derived from the Company's audited consolidated
financial statements. The financial data for the six months ended June 30, 1996
and 1995 are derived from the unaudited consolidated financial statements of the
Company. The unaudited financial statements include all adjustments, consisting
of normal recurring accruals, which the Company considers necessary for the fair
presentation of the financial position and results of operations for these
periods. Operating results for the six months ended June 30, 1996 are not
necessarily indicative of the results that may be expected for the entire year
ending December 31, 1996. The financial data set forth below should be read in
conjunction with the Company's Consolidated Financial Statements and Notes
thereto and "Management's Discussion and Analysis of Financial Condition and
Results of Operations" included elsewhere in this Prospectus.
 
     The pro forma consolidated statement of operations data for the six months
ended June 30, 1996 and the year ended December 31, 1995 give pro forma effect
to the Company's July 16, 1996 acquisition of EBT (including payments by the
Company for the EBT stock issuable upon exercise of outstanding EBT stock
options) as if such acquisition had occurred on January 1, 1996 and 1995,
respectively, and the pro forma consolidated balance sheet data at June 30, 1996
give pro forma effect to the EBT acquisition as if it had occurred on June 30,
1996. The pro forma statement of operations data for the six months ended June
30, 1996 and the year ended December 31, 1995 do not reflect a charge of
$34,300,000 for certain purchased in-process research and development to be
recorded by the Company in the third quarter of 1996. See the Company's Pro
Forma Consolidated Financial Information (Unaudited) appearing elsewhere herein.
 
<TABLE>
<CAPTION>
                                 PRO FORMA            SIX MONTHS            PRO FORMA
                                 SIX MONTHS         ENDED JUNE 30,         YEAR ENDED          YEAR ENDED DECEMBER 31,
                                 ENDED JUNE      --------------------       DECEMBER        ------------------------------
                                  30, 1996        1996         1995         31, 1995         1995        1994       1993
                                 ----------      -------      -------      -----------      -------     -------    -------
                                                         (IN THOUSANDS, EXCEPT PER SHARE AMOUNTS)
<S>                              <C>             <C>          <C>          <C>              <C>         <C>        <C>
STATEMENT OF OPERATIONS DATA:
Net revenues...................   $ 35,093       $27,605      $17,925        $57,201        $43,387     $23,463    $13,757
Cost of revenues...............      5,785         3,845        2,516          9,067          5,792       3,074      1,870
                                   -------       -------      -------        -------        -------     -------    -------
Gross profit...................     29,308        23,760       15,409         48,134         37,595      20,389     11,887
Total operating expenses.......     25,815        18,559       14,526         37,045         26,017      11,856      7,501
                                   -------       -------      -------        -------        -------     -------    -------
Operating income...............      3,493         5,201          883         11,089         11,578       8,533      4,386
Net investment income..........      1,479         1,533          337          1,432          1,468         319
                                   -------       -------      -------        -------        -------     -------    -------
Income before provision for
  income taxes.................      4,972         6,734        1,220         12,521         13,046       8,852      4,386
Income tax expense.............      3,676         4,014        2,583          7,042          7,052       3,189      1,811
                                   -------       -------      -------        -------        -------     -------    -------
Net income (loss)..............   $  1,296(1)    $ 2,720(1)   $(1,363)(2)    $ 5,479        $ 5,994(2)  $ 5,663    $ 2,575
                                   =======       =======      =======        =======        =======     =======    =======
Primary net income (loss)
  per share....................   $   0.09(1)    $  0.20(1)   $ (0.11)(2)    $  0.45        $  0.49(2)  $  0.48    $  0.22(3)
Weighted average shares
  outstanding..................     13,690        13,690       12,292         12,228         12,228      11,798     11,560(3)
</TABLE>
 
<TABLE>
<CAPTION>
                                                                    PRO
                                                                   FORMA       JUNE 30,              DECEMBER 31,
                                                                  JUNE 30,     --------     -------------------------------
                                                                    1996         1996        1995        1994        1993
                                                                  --------     --------     -------     -------     -------
                                                                                       (IN THOUSANDS)
<S>                                                               <C>          <C>          <C>         <C>         <C>
BALANCE SHEET DATA:
Working capital.................................................  $19,961      $57,538      $55,460     $15,522     $ 1,802
Deferred income tax benefit, net................................    3,910        3,803        3,847       4,175          --
Total assets....................................................   68,564       91,729       91,129      33,494       6,373
Stockholders' equity............................................   46,164       80,464       75,163      27,614          --
Net assets......................................................       --           --           --          --       3,238(4)
</TABLE>
 
                                       12
<PAGE>   13
 
- ---------------
(1) Acquisition-related charges for certain purchased technology under research
    and development at Imagemark Software Labs, Inc. (renamed INSO Kansas City
    Corporation), which was acquired by the Company in January 1996, reduced net
    income and net income per share for the six months ended June 30, 1996
    (actual and pro forma) by $4,400,000 and $0.32, respectively. See
    "Management's Discussion and Analysis of Financial Condition and Results of
    Operations."
(2) Acquisition-related charges for certain purchased technology under research
    and development at Systems Compatibility Corporation (renamed INSO Chicago
    Corporation), which was acquired by the Company in April 1995, reduced net
    income and net income per share for the six months ended June 30, 1995 and
    the year ended December 31, 1995 by $5,500,000 and $0.45, respectively. See
    "Management's Discussion and Analysis of Financial Condition and Results of
    Operations."
(3) Assumes that the 11,560,000 shares of Common Stock outstanding immediately
    after the Company's initial public offering were outstanding throughout
    1993.
(4) Net assets represent Houghton Mifflin's net investment in the Company during
    the time the Company operated as a division of Houghton Mifflin.
 
                                       13
<PAGE>   14
 
               MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL
                      CONDITION AND RESULTS OF OPERATIONS
 
RESULTS OF OPERATIONS
 
     The Company derives its revenues from royalties, including initial
nonrefundable royalties, from license arrangements with OEMs, one-time license
and annual software maintenance fees from site-license agreements with corporate
customers, and from one-time fees for direct licenses to consumers.
 
     Royalty revenues are earned in one of the following ways: as a percentage
of net revenues from product unit sales by licensees that incorporate the
Company's products, as a fixed per-unit royalty, or as a regular periodic fee
based on estimated shipments or usage over time. Royalty revenues are generally
recognized in the Company's financial statements in the quarter in which amounts
due to the Company have been determined. In the event that further substantial
support or performance obligations exist, revenues are recognized ratably as
earned. Revenues from initial nonrefundable royalty arrangements are recognized
at the time of product acceptance by the licensee if no significant obligation
relating to the underlying contract remains to be completed. Revenues from
corporate site-license agreements generally consist of a one-time license fee
based on the number of individual users licensed and an annual software
maintenance fee calculated as a percentage of the one-time fee. Payment of the
maintenance fee permits customers to receive updates and enhancements to the
software licensed for the duration of the maintenance agreement.
 
     Typical license terms provide for a non-exclusive two-to-three year license
grant limited to use with specified OEM products or on specified platforms. In
certain limited circumstances, typically involving Information Products, a
license may be exclusive for a specified platform or product type, subject to
the satisfaction of performance standards. When possible, the Company licenses
off-the-shelf versions of its products to customers, although the Company
sometimes performs custom product development for a fee.
 
     The Company generates a significant portion of its revenues from customers
outside the United States. Such revenues totaled $5,673,000, $4,216,000, and
$3,076,000, for the years ended December 31, 1995, 1994, and 1993, respectively.
The Company believes that a substantial amount of products shipped by its
domestic OEM customers is sold internationally. Accordingly, the actual use of
the Company's products by overseas end users is higher than the export revenues
reported for accounting purposes as described above. The Company expects that
the international market will continue to account for a significant portion of
its total business. The Company's export revenues are primarily denominated and
collected in U.S. dollars. The Company also denominates the prices for its
corporate and end-user products sold internationally in U.S. dollars. Business
with overseas end users may be subject to greater currency exchange rate risk in
the future.
 
     Cost of revenues primarily comprises royalty expense for the licensing of
technology, content databases, published reference works from Houghton Mifflin
and other third parties, and the amortization of capitalized product development
costs and intangible assets from the acquisitions and license agreements
described in Note 4 of Notes to the Company's Consolidated Financial Statements.
The level of amortization expense of capitalized product development costs is
directly related to the amount of product development costs capitalized in each
year and the time frame in which a specific product is available for general
release to customers. The royalty cost includes direct royalty obligations as
well as the amortization of royalty advances.
 
                                       14
<PAGE>   15
 
     The following table sets forth, for the periods indicated, certain income
statement data expressed as a percentage of revenues.
 
<TABLE>
<CAPTION>
                                                    SIX MONTHS
                                                  ENDED JUNE 30,       YEAR ENDED DECEMBER 31,
                                                  ---------------     -------------------------
                                                  1996      1995      1995      1994      1993
                                                  -----     -----     -----     -----     -----
<S>                                               <C>       <C>       <C>       <C>       <C>
Net revenues....................................  100.0%    100.0%    100.0%    100.0%    100.0%
Cost of revenues................................   13.9      14.0      13.3      13.1      13.6
                                                  -----     -----     -----     -----     -----
Gross profit....................................   86.1      86.0      86.7      86.9      86.4
Operating expenses:
  Sales and marketing...........................   17.9      14.7      15.1      15.7      19.0
  Product development...........................   19.2      18.4      17.3      20.1      21.3
  General and administrative....................   14.3      17.3      14.9      14.7      14.2
  Purchased in-process research and
     development................................   15.9      30.7      12.7      --        --
                                                  -----     -----     -----     -----     -----
Total operating expenses........................   67.3      81.1      60.0      50.5      54.5
                                                  -----     -----     -----     -----     -----
Operating income................................   18.8       4.9      26.7      36.4      31.9
Net investment income...........................    5.6       1.9       3.4       1.3      --
                                                  -----     -----     -----     -----     -----
Income before provision for income taxes........   24.4       6.8      30.1      37.7      31.9
Income tax expense..............................   14.5      14.4      16.3      13.6      13.2
                                                  -----     -----     -----     -----     -----
Net income (loss)...............................    9.9%     (7.6)%    13.8%     24.1%     18.7%
                                                  =====     =====     =====     =====     =====
</TABLE>
 
  SIX MONTHS ENDED JUNE 30, 1996, COMPARED TO SIX MONTHS ENDED JUNE 30, 1995
 
     Revenues.  Revenues for the six months ended June 30, 1996 increased
$9,680,000, or 54.0%, to $27,605,000 compared to $17,925,000 for the six months
ended June 30, 1995. Royalty revenues increased 26.8% due primarily to higher
revenues from existing licenses of GCS, IntelliScope, ImageStream, and Outside
In. Contributing to the increase in royalty revenues were revenues from the INSO
Chicago Corporation ("INSO Chicago") and INSO Kansas City Corporation ("INSO
Kansas City") acquisitions as well as higher revenues from existing licensees.
Non-refundable royalty revenues in the first six months of 1996 more than
doubled over the same period in 1995, reflecting new licenses of the Information
Please almanacs; Dutch, Italian, Spanish, German, and French bilingual
dictionaries; ImageStream; and Outside In. Direct and retail sales of Quick View
Plus, CyberSpell, InWords, and SciWords also contributed to the overall increase
in total revenues.
 
     Gross Profit.  Gross profit increased $8,351,000 to $23,760,000 for the six
months ended June 30, 1996 from $15,409,000 for the six months ended June 30,
1995. Gross profit as a percentage of revenues for the six months ended June 30,
1996 was 86.1% compared to 86.0% for the six months ended June 30, 1995. The
increase in gross profit percentage was primarily attributable to higher
revenues from ImageStream and Outside In, which carry lower royalty burdens,
partially offset by higher amortization of license fees and other intangibles.
 
     Sales and Marketing.  Sales and marketing expenses consist primarily of
commissions on sales; salaries of sales, marketing, and technical support
personnel; and promotional expenses. Sales and marketing expenses increased
$2,293,000 to $4,927,000 for the six months ended June 30, 1996, reflecting
staff additions in sales as the Company establishes its presence in the
corporate sales channel and staff additions in the product management area to
support new product development. Sales and marketing expenses increased as a
percentage of revenues to 17.9% for the six months ended June 30, 1996 from
14.7% for the six months ended June 30, 1995.
 
     Product Development.  Product development expenses consist primarily of
personnel costs and, to a lesser extent, fees paid for outside software
development and consulting services. Product development expenses increased
$1,990,000 due to revisions to, and new product development for, the Company's
Proofing Tools, Information Products, and Information Management Tools product
lines. The Company's total product development costs, including capitalized
costs, were $6,146,000,
 
                                       15
<PAGE>   16
 
or 22.3% of revenues, for the six months ended June 30, 1996 compared to
$3,863,000, or 21.6% of revenues, for the six months ended June 30, 1995. New
products released during the first six months of 1996 included Cyberspell,
SciWords, InWords, the electronic versions of The 1996 Information Please
Almanac and The Information Please Sports Almanac, IntelliScope search enhancer
for Japanese, Inso Search Wizard, ImageStream for Microsoft Office, and Quick
View Plus plug-in for Netscape Navigator 2.0.
 
     General and Administrative.  General and administrative expenses increased
$850,000 to $3,951,000 for the six months ended June 30, 1996 compared to
$3,101,000 for the six months ended June 30, 1995. The increase in general and
administrative expenses was primarily attributable to increases in personnel and
general corporate expenses required to support the growth of the Company's
operations. General and administrative expenses declined as a percentage of
revenues to 14.3% for the six months ended June 30, 1996 from 17.3% for the six
months ended June 30, 1995 as a result of improved efficiencies and economies of
scale in the administrative area.
 
     Purchased In-Process Research and Development.  The acquisition of INSO
Kansas City and INSO Chicago, respectively, included the purchase of certain
technology under research and development, which resulted in a charge to the
Company's June 30, 1996 and 1995 consolidated results of $4,400,000, or $0.34
per share and $5,500,000, or $0.44 per share, respectively.
 
     Income Taxes.  The Company's effective tax rate for the six months ended
June 30, 1996 and 1995 was influenced by the $4,400,000 INSO Kansas City and the
$5,500,000 INSO Chicago research and development charges discussed above. The
charges were not deductible for tax purposes. Excluding the charges, the
Company's effective tax rate for the six months ended June 30, 1996 was 36.1%
compared to 38.4% for the six months ended June 30, 1995.
 
     Net Income.  Excluding the $4,400,000 ($0.34 per share) in-process research
and development charge related to the INSO Kansas City acquisition in the six
months ended June 30, 1996 and the $5,500,000 ($0.44 per share) in-process
research and development charge related to the INSO Chicago acquisition in the
six months ended June 30, 1995, net income and earnings per share would have
been $7,120,000 and $0.52, respectively, for the six months ended June 30, 1996,
compared to $4,137,000 and $0.34, respectively, for the six months ended June
30, 1995.
 
  YEAR ENDED DECEMBER 31, 1995, COMPARED TO YEAR ENDED DECEMBER 31, 1994
 
     Revenues.  Revenues for 1995 increased $19,924,000, or 84.9%, to
$43,387,000, including $1,500,000 of non-recurring revenues earned from royalty
audits, compared to $23,463,000 for 1994.
Revenues in 1995 included revenues from the acquisition of INSO Chicago since
the acquisition date of April 1, 1995. See Note 4 of Notes to the Company's
Consolidated Financial Statements. Revenues from INSO Chicago accounted for
approximately 20% of the total in 1995. Royalty revenues increased 71.1%,
including the revenues earned from royalty audits, as a result of increased
sales by existing licensees as well as the number of licensees making royalty
payments, which increased to 110 from 82 at December 31, 1994. Royalty revenues
increased 62.7%, excluding the $1,500,000 non-recurring royalty audit revenues.
The increase in the number of licensees making royalty payments reflects new
licensees resulting from the INSO Chicago acquisition, as well as royalty flow
from existing licensees who have earned their prepaid minimum royalties. In
particular, continuing sales of Microsoft's Word and Office products, which
incorporate the Company's CorrecText and International CorrectSpell, contributed
substantially to gains in revenues. Nonrefundable royalty revenues for 1995
increased 77.9%, reflecting the addition of 149 new licenses in 1995 compared to
109 new licenses in 1994. New licensees for 1995 included InterGO
Communications, Inc. (formerly TeacherSoft Corporation), America Online, Inc.,
AT&T New Media Services, Bloomberg, L.P., the European Commission, and Starwave
Corporation. During 1995, the Company released additional languages for
International CorrectSpell, IntelliScope, International ProofReader,
CorrectEnglish, and concise electronic thesaurus. Also released during 1995 were
new versions of Quick View Plus, IntelliFinder, and Dutch, French, Italian, and
Spanish bilingual
 
                                       16
<PAGE>   17
 
dictionary databases, as well as electronic versions of The 1996 Information
Please Business Almanac and The 1996 Information Please Entertainment Almanac.
 
     Gross Profit.  Gross profit as a percentage of revenues was 86.7% in 1995
compared to 86.9% in 1994. Amortization of capitalized software and intangibles
increased as a percentage of revenues in 1995 as a result of the release of new
languages of CorrectEnglish, International ProofReader, concise electronic
thesaurus, and IntelliScope; numerous reference works; and a new version of
Quick View Plus; as well as amortization of costs related to the INSO Chicago
acquisition and rights related to the Information Please almanac series. This
increase in amortization was more than offset by lower royalty costs as a
percentage of revenue as a greater proportion of 1995 revenues was derived from
the CorrecText, Outside In, and Quick View Plus products, which carry lower
royalty burdens.
 
     Sales and Marketing.  Sales and marketing expenses for 1995 increased 78.7%
to $6,570,000 from $3,676,000 for 1994, reflecting increased staff due to the
INSO Chicago acquisition, entry into new markets (corporate and consumer), staff
additions in product management to support the higher levels of sales, and
higher commissions due to increased revenues.
 
     Product Development.  Product development expenses increased 58.4% to
$7,489,000 for 1995 from $4,728,000 for 1994. The increase in product
development costs was primarily due to investments in CorrectEnglish,
International ProofReader, IntelliScope, Quick View Plus, IntelliFinder,
CyberSpell, Inso Search Wizard, and various reference works. As a percentage of
revenues, product development expenses decreased to 17.3% in 1995 from 20.1% for
1994. The decrease as a percentage of revenues was primarily attributable to
non-labor costs that represented a lower percentage of revenues in 1995 compared
to 1994. This decrease was partially offset by capitalized development costs for
IntelliScope, CorrectEnglish, Quick View Plus, Inso Search Wizard, concise
electronic thesaurus, and bilingual dictionary databases that approximated 1994
in terms of dollars but represented a lower percentage of development expenses
(15.4% in 1995 versus 22.2% in 1994). The Company's total product development
costs, including capitalized costs, were $8,853,000, or 20.4% of revenues, for
1995, compared to $6,080,000, or 25.9% of revenues, for 1994.
 
     General and Administrative.  General and administrative expenses in 1995
increased 87.1% to $6,458,000 from $3,452,000 in 1994. The increase in general
and administrative expenses was primarily attributable to increases in personnel
and general corporate expenses required to support the growth of the Company's
operations. General and administrative expenses increased only slightly as a
percentage of revenues to 14.9% for 1995 compared with 14.7% for 1994.
 
     Purchased In-Process Research and Development.  The acquisition of INSO
Chicago included the purchase of certain technology under research and
development, which resulted in a charge to the Company's 1995 consolidated
results of $5,500,000, or $0.44 per share.
 
     Income Taxes.  The Company's effective tax rate was influenced by the
$5,500,000 INSO Chicago research and development charge discussed above. The
charge was not deductible for tax purposes. Excluding the charge, the Company's
effective tax rate in 1995 was 38.0% compared to 36.0% in 1994. The increase is
a result of the increased profitability causing a shift to a higher tax bracket
as well as amortization of the intangible assets from the INSO Chicago
acquisition, which are not deductible for income tax purposes.
 
     Net Income.  Excluding the INSO Chicago research and development charge
noted above, net income and earnings per share would have been $11,494,000 and
$0.94 per share, respectively.
 
  YEAR ENDED DECEMBER 31, 1994, COMPARED TO YEAR ENDED DECEMBER 31, 1993
 
     Revenues.  Revenues for 1994 increased $9,706,000, or 70.6% to $23,463,000
compared to $13,757,000 for 1993. Royalty revenues were up 70.3% as a result of
increased sales by existing licensees as well as the number of licensees making
royalty payments, which increased to 82 from 50 at December 31, 1993. The
increase in the number of licensees making royalty payments reflects
 
                                       17
<PAGE>   18
 
new licensees resulting from the Microlytics, Inc. license agreement, described
in Note 4 of Notes to the Company's Consolidated Financial Statements, as well
as royalty flow from existing licensees that have earned out the amount of their
prepaid minimum royalties. In particular, continuing sales of Microsoft's Word
and Office products, which incorporate the Company's CorrecText and
International CorrectSpell, contributed substantially to the gains in revenues.
Nonrefundable royalty revenues for 1994 increased 71.3%, reflecting the addition
of 109 new licenses in 1994 compared to 71 new licenses in 1993. New licensees
for 1994 included Dataware Technologies, MINDSCAPE, Ligature, NOVA, Catena,
Digital Communications Associates, and Gold Disk. During 1994, the Company
released CorrectEnglish in French and German, as well as International
ProofReader and IntelliScope, which is the first product in the Company's new
line of Information Management Tools. In addition, new versions of International
CorrectSpell and IntelliFinder were released in 1994.
 
     Gross Profit.  Gross profit as a percentage of revenues was 86.9% in 1994
compared to 86.4% in 1993. Amortization of capitalized software and software
licenses increased in 1994 as a result of the release of new products such as
CorrectEnglish, International ProofReader, IntelliScope, and numerous reference
works, as well as the Microlytics, Inc. license. This increase in amortization
was more than offset by lower royalty costs that resulted from a greater
proportion of 1994 revenues being derived from the CorrecText and IntelliScope
products, which carry lower royalty burdens.
 
     Sales and Marketing.  Sales and marketing expenses for 1994 increased 40.7%
to $3,676,000 from $2,612,000 for 1993, reflecting increased market research and
staff additions in product management to support the higher levels of sales as
well as higher commissions due to increased revenues.
 
     Product Development.  Product development expenses increased 61.3% to
$4,728,000 for 1994 from $2,932,000 for 1993. The increase in product
development costs was primarily due to investments in CorrectEnglish,
International ProofReader, reference works, and development of the Company's new
line of Information Management Tools, including IntelliScope, which was released
on schedule in mid-1994. As a percentage of revenues, product development
expenses decreased to 20.1% for 1994 from 21.3% for 1993. The decrease as a
percentage of revenues was partially attributable to capitalization of a
slightly higher proportion of development expenses (22.2% in 1994 versus 21.6%
in 1993) in 1994 reflecting the IntelliScope and CorrectEnglish development.
Also contributing to the decrease was containment of non-labor costs
representing a lower percentage of revenues in 1994 compared to 1993. The
Company's total product development costs, including capitalized costs, were
$6,080,000, or 25.9% of revenues, for 1994, compared to $3,738,000, or 27.2% of
revenues, for 1993.
 
     General and Administrative.  General and administrative expenses in 1994
increased 76.4% to $3,452,000 from $1,957,000 in 1993. The increase in general
and administrative expenses was primarily attributable to increases in personnel
and general corporate expenses required to support the growth of the Company's
operations. General and administrative expenses increased only slightly as a
percentage of revenues to 14.7% for 1994 compared to 14.2% for 1993.
 
     Income Taxes.  The Company's effective tax rate in 1994 was 36.0% compared
to 41.3% in 1993. The decrease in the effective rate reflects the benefit from
the valuation of the deferred tax asset resulting from the formation of the
Company.
 
LIQUIDITY AND CAPITAL RESOURCES
 
     The Company's operating activities have provided cash of $6,859,000 for the
six months ended June 30, 1996 and $19,720,000, $6,852,000, and $1,404,000 for
the years ended December 31, 1995, 1994, and 1993, respectively.
 
     The Company's investing activities have used cash of $33,005,000 for the
six months ended June 30, 1996 and $36,611,000, $6,415,000, and $1,031,000 for
the years ended December 31, 1995, 1994, and 1993, respectively. Of these
amounts, $865,000, $1,364,000, $1,352,000, and $806,000 respectively, were for
capitalized product development costs as discussed above. Cash used for
 
                                       18
<PAGE>   19
 
investing activities during the six months ended June 30, 1996 reflects the
January 9, 1996 acquisition of all of the outstanding capital stock of INSO
Kansas City for net cash of $6,492,000. The increase in investing activities in
1995 reflects investments in marketable securities totaling $25,397,000 and two
acquisitions completed during 1995 for $7,639,000 in cash. Also contributing to
the increased investing activities were additional investments in leasehold
improvements, furniture, and equipment related to the Company's move of its
corporate headquarters, completed at the end of April 1995.
 
     The Company's financing activities used cash of approximately $4,777,000
for the six months ended June 30, 1996 and provided cash of $40,268,000 and
$13,421,000 for the years ended December 31, 1995 and 1994, respectively. As
part of the INSO Chicago acquisition in April 1995, the Company issued
promissory notes in the amount of $6,367,500, which were repaid in full in
February 1996 from available cash. In August 1995, the Company completed a
public offering of 1,200,000 shares of the Company's common stock, which
provided net proceeds of approximately $39,300,000.
 
     The Company had available to it a deferred income tax benefit in the amount
of $9,456,000 as of June 30, 1996, which is recorded at the net amount of
$4,648,000 after deduction of a valuation allowance in the amount of $4,808,000.
This benefit relates to a basis difference between assets reported in the
Company's financial statements and for income tax purposes, primarily tax basis
intangible assets arising in connection with the formation of the Company and
completion of its initial public offering. The tax benefit is subject to
statutory realization ratably over a remaining 13-year period and, as a result,
the Company's prospective cash requirement for income taxes may be reduced by
approximately $700,000 per year. The amount of the tax benefit ultimately
recovered is dependent upon the amount of taxable income earned by the Company
both annually and over the 15-year period following the initial public offering
of the Company's common stock. Therefore, there can be no assurance that all or
some portion of the annual cash requirement reduction, or the full amount of the
tax benefit relative to the asset basis differential, will be realized.
 
     As of June 30, 1996, the Company had working capital of $57,538,000. Cash,
cash equivalents, and marketable securities as of June 30, 1996 totaled
$55,910,000. On July 16, 1996, the Company acquired all of the outstanding
capital stock of EBT. In connection with the EBT acquisition, the Company paid
$27,800,000 in cash in July 1996 and is obligated to pay an additional
$1,500,000 to the former principal stockholder of EBT in January 1998 and up to
an additional $10,400,000 to purchase EBT stock issuable upon exercise of
outstanding EBT stock options. The purchase price is expected to be paid from
available cash and marketable securities. In the event that certain EBT
financial and operating goals are met, contingent payments of up to an
additional $5,300,000 are also expected to be paid from available cash and
marketable securities. The Company believes that the proceeds of this offering,
together with funds expected to be generated from operations, will be sufficient
to finance the Company's operations for the foreseeable future.
 
INFLATION
 
     The Company does not believe that inflation has had a significant impact on
its results of operations for the periods presented.
 
                                       19
<PAGE>   20
 
                                    BUSINESS
 
     The Company is a leading provider of multilingual software products and
systems that help people correct, find, view, publish, and distribute data,
text, and images in electronic environments ranging from individual desktops to
the Internet. The Company markets certain of its products worldwide to OEMs of
computer hardware, software, and consumer electronics products. The Company also
markets software applications and systems to major corporations, government
agencies and end users. The Company currently has nearly 450 OEM customers and
over 600 direct corporate licensees, and the Company believes that the worldwide
installed base of end-user licensees of OEM products incorporating INSO's
technology exceeds 50,000,000.
 
CORE TECHNOLOGIES
 
     The Company draws on proprietary technologies in areas such as linguistic
and data analysis to create products focused on the needs of each of the
Company's markets. The Company has assembled a team of distinguished experts in
the fields of linguistics, data analysis, and document structuring and has
extensive experience in developing its technologies into software products.
 
     The Company's core technologies are distinguished by a combination of four
core competencies:
 
     - Computational Linguistics and Lexicography.  Computational linguistics is
       a scientific discipline concerned with the analysis of the patterns and
       irregularities of languages, and the encoding of those properties so that
       language can be efficiently processed by computer. Lexicography is the
       process or work of compiling and analyzing words in order to create a
       dictionary.
 
     - Software Engineering.  The creation of efficient software code for
       language and data analysis supporting numerous computing platforms.
 
     - Information Base Technology.  Techniques and tools for structuring,
       indexing, and compressing raw or formatted data, text, graphics and other
       content elements to facilitate the building of either proprietary or
       open, standards-compliant databases for efficient and customizable access
       to and retrieval of information.
 
     - Document Structure Knowledge.  Techniques and processes that interrogate,
       analyze, and process text, graphics, and other content elements within
       software application files and provide file access, viewing, and
       conversion.
 
BUSINESS STRATEGY
 
     The Company's strategy is to concentrate its development and marketing
efforts on building and promoting solutions where the combination of its core
competencies can create substantial added value and to optimize those solutions
for markets and market segments where the Company can achieve a significant
position. Key elements of this strategy include:
 
     Extend Technological Lead in Core Competencies.  The Company strives to
extend the depth of its core competencies. For example, in 1994, through its
research and development efforts with respect to the technologies underlying
IntelliScope, the Company expanded its linguistic core competencies to include
sentence structure analysis in all major European languages. The Company has
continued to expand its linguistics capabilities, and in 1996 released
IntelliScope in Japanese, beginning the extension of its linguistic core
competency to Asian languages. Similarly, in 1995 the Company began to expand
its core competencies to include the management of search queries. Through a
combination of computational linguistic techniques and information base
technology, the Company developed during 1996 the Inso Search Wizard query
refinement tool that limits the query to the specific subject matter area that
the user selects, and then expands the query within that subject matter area by
also searching on related terms.
 
                                       20
<PAGE>   21
 
     Diversify Product Offerings and Product Lines.  The Company seeks to
diversify its sources of revenue through the addition of products in existing
markets and the introduction of products in new and emerging markets. In 1994,
the Company added the Columbia Encyclopedia, Fifth Edition and the Concise
Columbia Electronic Encyclopedia to its Information Products reference line. In
1995, the Company further expanded its Information Products through the
acquisition of the Information Please almanacs and the addition of three new
titles to the Information Please line.
 
     The Company also seeks to diversify its product offerings through the
addition of products intended for distribution through alternative channels. In
1996, the Company introduced CyberSpell, a Netscape Navigator plug-in proofing
technology for electronic and retail distribution, and ImageStream for Microsoft
Office, a graphics conversion utility intended for direct, electronic, and
retail distribution.
 
     Expand Distribution Channels.  The Company has expanded its customer base
through the use of multiple distribution channels. In 1995, the Company began
marketing Quick View Plus directly to corporate users and, through software
distribution channels, to consumers. Also during 1995, the Company opened its
European headquarters to manage the marketing of its products directly to
corporations and consumers in the European market. To complement its existing
reseller and distributor channels, the Company has recently commenced the direct
marketing of certain products to end users through electronic means.
 
     In 1996, the Company substantially strengthened its direct corporate
selling activity and began a concentrated government sales effort. At the same
time, the Company has significantly expanded its relationships with distributors
and resellers of computer software, and has added marketing resources dedicated
to the development of the direct and consumer channels throughout the world.
 
     Accelerate Growth and Strengthen Core Competencies Through
Acquisitions.  In 1995, the Company acquired Systems Compatibility Corporation
(subsequently renamed INSO Chicago), which was at that time a leading supplier
of file viewing technologies to the software industry. This acquisition expanded
the Company's revenue base and provided a significant new core competency in
document structure knowledge and strengthened the Company's competency in
software engineering. At the same time, the Company acquired a corporate sales
presence in order to diversify its distribution channels. In January 1996, the
Company acquired Imagemark Software Labs, Inc. (subsequently renamed INSO Kansas
City), which added to the depth of the Company's document structure knowledge
and further expanded its revenue base. The INSO Kansas City acquisition also
gave the Company a leading position in the graphics conversion market,
reflecting the use of INSO Kansas City's graphics filters by leading developers
of software applications in the United States.
 
     Similarly, through the acquisition of EBT (renamed INSO Providence), the
Company has substantially increased the depth of its information base technology
and document structure knowledge. In addition, this acquisition has diversified
both the Company's product offerings and its distribution channels by adding a
significant new product line and a substantial base of new corporate,
government, and international customers.
 
                                       21
<PAGE>   22
 
PRODUCTS
 
     The Company offers a diverse array of products and solutions targeting
multiple distribution channels and market segments within the software industry.
The Company's product strategy is to leverage its linguistic, document and data
structuring, and software engineering expertise into fast, efficient, and
portable software products and solutions targeted at specific user needs. The
Company's products are divided into four major categories: Proofing Tools,
Information Management Tools, Information Products, and Electronic Publishing
Solutions.
 
  Proofing Tools
 
     The Company's Proofing Tools product line includes software programs and
related databases for correcting errors in spelling, grammar, punctuation,
capitalization, spacing, and other mistakes in documents created by users of
computer applications. The Company's Proofing Tools products include OEM
products such as International CorrectSpell, the industry-standard spelling
correction system; International ProofReader, a multilingual proofreading system
available in 10 languages that addresses numerous classes of writing errors and
style problems; and CorrectText Grammar Correction System, the leading English
grammar correction technology used in word processors today. Examples of
products using the Company's Proofing Tools include Microsoft's Word and Office,
Lotus Development Corporation's WordPro, SmartSuite, and Notes, and a version of
Netscape Communications Corporation's Powerpack.
 
     The Company's newest Proofing Tool, CorrectEnglish, is a writing system
targeting the specific errors made by native speakers of Chinese, French,
German, Japanese, and Spanish when producing English language documents. This
product is designed to capitalize on the growing trend toward the use of English
as the international commercial language, and makes use of the Company's
linguistic expertise in both English and foreign languages by combining English
spelling, proofing and grammar correction with error messages and correction
instructions in the user's native language.
 
                                 PROOFING TOOLS
 
<TABLE>
<CAPTION>
- -----------------------------------------------------------------------------------------
                    PRODUCT                                 DESCRIPTION
     --------------------------------------    -------------------------------------
<S>                                            <C>                                  
           International CorrectSpell             24-language spelling correction
           International ProofReader              10-language proofreading system
     CorrectText Grammar Correction System          English grammar correction
                                                            technology
                 CorrectEnglish                English as a second language writing
                                                              system
                    SciWords                     Scientific and technical spelling
                                                           dictionaries
                    InWords                         Add-on spelling dictionary
                   CyberSpell                    Text-proofing add-on product for
                                                   Internet e-mail applications
- -----------------------------------------------------------------------------------------
</TABLE>
 
  Information Management Tools
 
     The Company's Information Management Tools product line includes search and
indexing enhancement products and file filtering, viewing, and conversion
products. The Company's search enhancement products are based on the ability of
the Company's technologies to analyze and process linguistic information. These
products are designed to bring the Company's linguistic expertise to bear on the
increasingly difficult problem of accurate searching and indexing of information
across desktops, LANs, WANs, and the World Wide Web, and include IntelliScope, a
 
                                       22
<PAGE>   23
 
multilingual tool that performs linguistic analysis, and Inso Search Wizard, an
interactive search expansion and refinement utility.
 
     The Company's file filtering, viewing and conversion products are based on
the Company's document structure knowledge and the ability of the Company's
software programs to use that knowledge to render or convert information within
documents quickly and accurately. These products are designed to fulfill the
need for access to text, images and data created in a variety of formats as the
amount and complexity of documents stored and transmitted in electronic format
continues to increase, and include the Outside In OEM viewing technology; the
Quick View Plus end-user product, an application that provides corporations and
consumers with the ability to view, export, copy, and print files originating in
any of over 200 applications; the ImageStream graphics filters OEM product,
which permits the exchange of graphical images among more than 60 charting,
presentation, and graphical applications; and the CADleaf computer assisted
design file format viewing, conversion, and annotation utility.
 
     Some examples of products using the Company's Information Management Tools
include Microsoft's Windows 95, Fulcrum Technology Inc.'s SearchServer, and
Novell, Inc.'s GroupWise.
 
                          INFORMATION MANAGEMENT TOOLS
- --------------------------------------------------------------------------------
 
<TABLE>
<CAPTION>
             PRODUCT                             DESCRIPTION
- ---------------------------------    ------------------------------------
<S>                                  <C>
          Intelliscope                 15-language search and indexing
                                               enhancement tool
       Inso Search Wizard              Interactive search expansion and
                                              refinement utility
           Outside In                  OEM file viewing and data access
                                                  technology
         Quick View Plus              End-user file viewing application
           ImageStream                 OEM graphical file filtering and
                                            conversion technology
ImageStream for Microsoft Office     End-user Office-compatible graphics
                                              conversion utility
             CADleaf                 Viewing, conversion, and annotation
                                     utility for computer assisted design
                                        and manufacturing file formats
</TABLE>
 
- --------------------------------------------------------------------------------
 
  Information Products
 
     The Company's Information Products product line utilizes the Company's
information base technology and lexical expertise to produce electronic
reference works that combine authoritative, current content with advanced
electronic search capabilities. Through its ownership of information databases
and use of internal editorial resources, the Company creates proprietary content
designed for distribution through electronic means. The Company also licenses
authoritative content from information providers around the world, including
major print publishers, as the bases for additional Information Products. The
Information Products line includes more than 60 reference titles, including The
Columbia Encyclopedia, Fifth Edition, The Concise Columbia Electronic
Encyclopedia, and the American Heritage dictionaries. The Company's Information
Products also include reference products developed from its proprietary
information databases. Certain of these products are published in print form as
the Information Please almanacs and the A&E Entertainment Almanac. The Company
anticipates that it will continue to add to its proprietary information
databases and produce new reference products from those databases. Examples of
products using the Company's Information Products include Microsoft's Bookshelf,
CompuServe, Inc.'s CompuServe Information Service, Starwave Corporation's ESPNET
SportsZone, InterGO Communications, Inc.'s
 
                                       23
<PAGE>   24
 
InterGO, AT&T New Media Services' AT&T Business Network, and Bloomberg L.P.'s
THE BLOOMBERG.
 
                              INFORMATION PRODUCTS
 
<TABLE>
    <S>                                        <C>
    ------------------------------------------------------------------------------------
                     PRODUCT                                  DESCRIPTION
            Information Please series            General, Business, Sports, Kids' and
                                                     Girls' almanacs, and the A&E
                                                         Entertainment Almanac
            Monolingual dictionaries,                Standard language references
         including the American Heritage
                  dictionaries
             Bilingual dictionaries               Bi-directional language references
    The Columbia Encyclopedia, Fifth Edition            Information references
         The Concise Columbia Electronic
                  Encyclopedia
                  IntelliFinder                     Software information retrieval
                                                         program for use with
                                                         Information Products
    ------------------------------------------------------------------------------------
</TABLE>
 
  Electronic Publishing Solutions
 
     The Company's Electronic Publishing Solutions feature the DynaText
publishing system, which is composed of automated and interactive tools to
create structured content from commonly used word processing and page makeup
systems, and browsing technology which permits users to select from among
specific views and structures to personalize the retrieval and presentation of
data. These products allow major corporations and government users to distribute
and maintain complex documents in many languages through multiple media such as
print, CD-ROM, LANs, WANs, and the World Wide Web.
 
                        ELECTRONIC PUBLISHING SOLUTIONS
 
<TABLE>
    <S>                                        <C>
    ------------------------------------------------------------------------------------
                     PRODUCT                                  DESCRIPTION
                    DynaText                         Electronic publishing system
                     DynaTag                           SGML structuring utility
                     DynaWeb                         Web publishing extension to
                                                               DynaText
    ------------------------------------------------------------------------------------
</TABLE>
 
MARKETING, SALES, AND DISTRIBUTION
 
     The Company markets its products worldwide to OEMs of computer software,
hardware, and consumer electronic products; corporations and government
agencies; and end users. The Company currently has nearly 450 OEM customers and
over 600 direct corporate licensees, and the Company believes that the worldwide
installed base of end-user licensees of OEM products incorporating INSO's
technology exceeds 50,000,000. The Company markets its products directly to OEMs
through its dedicated account management staff. The Company also markets its
products to corporations and government agencies directly and through resellers
and distributors, both domestically and overseas. The Company also markets and
sells certain products directly and indirectly to end users through electronic
means, to complement its existing reseller and distributor channels.
 
                                       24
<PAGE>   25
 
     The Company's sales and marketing organization, consisting of approximately
130 individuals, is managed from the Company's headquarters in Boston,
Massachusetts, and includes sales representatives or account managers in several
major markets worldwide. The Company conducts its OEM sales through a dedicated
account management program for large customers and through worldwide new
business development efforts. New business development efforts for OEM sales are
focused on identifying potential new applications and markets for the Company's
OEM products. The Company's corporate and governmental sales efforts are
conducted through sales forces dedicated to the Company's end-user products,
both directly and indirectly.
 
     The Company, through its various subsidiaries, currently has operations in
many major European countries, as well as Japan and Australia. These operations
manage sales of the Company's products to end users, both directly and through
networks of value-added resellers and distributors, as well as to OEMs.
 
KEY CUSTOMERS
 
     For the year ended December 31, 1995, five of the Company's customers
accounted for 67% (64%, if certain non-recurring revenue earned from royalty
audits is excluded) of its revenues, compared to 69% of its revenues for the
year ended December 31, 1994. A loss of, or significant decline in, revenues
from any key customer could have a material adverse effect on the Company's
business, financial condition, and results of operations.
 
     For the year ended December 31, 1995, Microsoft accounted for 52% (50%, if
certain non-recurring revenue earned from royalty audits is excluded) of the
Company's revenues compared to 55% for 1994. Most of the revenues received by
INSO from Microsoft derive from the use of INSO's Proofing Tools in Microsoft's
Word and Office products. During 1995, the Company amended its agreement with
Microsoft with respect to Proofing Tools. Under the terms of the amended
agreement, the Company has granted to Microsoft, for substantially equal fixed
quarterly minimum payments in 1996 and 1997, (i) a license to use version 3.02
of INSO's grammar product (the "Licensed Grammar Product") in specified versions
of Microsoft's Word and Office products and (ii) an unlimited license to use a
version of INSO's spelling and thesaurus products in all Microsoft products.
Depending on the versions of Word and Office in which Microsoft uses the
Licensed Grammar Product after June 30, 1996, INSO can earn additional
predetermined revenues ("Usage Fees") through the termination date of the
agreement (March 2001). INSO expects that its revenues for the third quarter of
1996 will include certain such Usage Fees. There can be no assurance, however,
that INSO will receive any revenues from Microsoft after December 1997 with
respect to the Licensed Grammar Product. See "Risk Factors -- Reliance on Key
Customers."
 
RESEARCH AND DEVELOPMENT
 
     The Company operates in an industry that is subject to rapid technological
change, and its ability to compete and operate successfully depends on, among
other factors, its ability to anticipate such change. Accordingly, the Company
is committed to the development of new products and the continuing evaluation of
new technologies. In addition, the Company is currently developing new products
for use on or in conjunction with the Internet and the World Wide Web. The rapid
changes that characterize these markets may require that the Company make
substantial additional investments in research and development in order to
respond to unforeseen market or technological developments. During the six
months ended June 30, 1996, and during 1995, 1994, and 1993, the Company's
expenditures for developing new products and product enhancements were
$6,146,000, $8,853,000, $6,080,000, and $3,738,000, respectively. These
expenditures represented 22%, 20%, 26%, and 27%, respectively, of total revenues
for those periods. Of these amounts, $865,000, $1,364,000, $1,352,000, and
$806,000, respectively, were capitalized in accordance with applicable
accounting principles and are subject to amortization over subsequent periods.
The balance was charged as product development expense.
 
                                       25
<PAGE>   26
 
COMPETITION
 
     The market for Proofing Tools is characterized by a relatively small number
of participants marketing primarily through OEM channels. In addition to the
Company, the principal participants in the Proofing Tools market include
SoftArt, Inc. and WordPerfect Corporation, now a subsidiary of Novell, Inc.,
which, following the sale of its word processing and office suite software
products to Corel Corporation, has licensed its linguistic technology to
software developers on an OEM basis. The Company also could face competition
from Microsoft or any other OEM customer that were to develop internally its own
products comparable to the products currently licensed from the Company.
 
     Competition in the markets for the Company's Information Management Tools
is significant. The Company's search enhancement products compete with products
offered by an affiliate of Xerox Corporation, and potentially compete with
offerings from other software development organizations with the capacity and
expertise to enter this market. The Company believes that as it continues to
introduce products focusing on query refinement and expansion, including concept
searching, it will face significant competition. The Company believes that the
principal competitive factors in these markets are product quality and
compatibility with multiple applications, with price being a secondary factor.
The Company's file-viewing technologies face competition from affiliates of
Adobe Systems, Inc. ("Adobe") in the OEM market and FTP Software Corporation in
the direct and retail markets. The Company's current graphics file conversion
products face competition from a number of smaller organizations, each
specializing in certain formats or applications. The Company expects that as it
broadens its file-viewing and conversion product line to include formats such as
HTML, it will encounter significant competition from a large number of
participants. The Company also faces limited competition in certain market
segments from large companies such as Oracle Corporation and International
Business Machines Corporation.
 
     There is a large number of participants in the market for the Company's
Information Products, none of which has a dominant market position. Participants
in parts of this market segment include Franklin Electronic Publishers, Inc. and
Random House Electronic Publishing, Inc. (electronic dictionaries); Compton's
NewMedia, Inc. and Groliers Electronic Publishing, Inc. (electronic
encyclopedias); and Microsoft (Information Products generally). In addition, in
certain language markets, the Company may face competition from information
products developed by or for print publishers having substantial name
recognition in such markets.
 
     The market for Electronic Publishing Solutions is characterized by a
limited number of large participants offering full or partial solutions, based
largely on proprietary formats. Participants in this market include Adobe and
its affiliates, Interleaf, Quark, and SoftQuad. In addition, as the market for
electronic publishing solutions grows, the Company expects to face additional
competition from participants offering standards-based solutions, such as those
offered by the Company.
 
     The Company believes that the principal competitive factors in the markets
for its principal products are product quality, ease of use, platform support,
and price. An additional competitive factor in the market for Proofing Tools is
language coverage.
 
     Some of the Company's competitors and potential competitors have
substantially greater development, marketing, sales, and financial resources
than the Company.
 
THIRD-PARTY DATABASE AND CONTENT SUPPLY ARRANGEMENTS
 
     The Company's Proofing Tools and Information Products, and certain of its
Information Management Tools, products typically combine a database (such as a
word list or a general reference database) with proprietary software technology.
These databases are generally acquired through licensing arrangements with
domestic and international third-party sources, typically print publishers and
universities, although a number of such databases are owned by the Company. The
Company seeks to work with leading, authoritative content sources in each of its
product and market
 
                                       26
<PAGE>   27
 
segments. The Company has arrangements in place with more than 40 publishers and
other information suppliers.
 
     For its Proofing Tools and Information Management Tools product lines, the
Company acquires both word lists and full-definition databases. For its
Information Products line, the Company generally acquires selected electronic
rights for the underlying works on which the products are based. The Company
owns the copyrights to the databases used in its English-language Proofing Tools
and Information Management Tools products.
 
     Although terms vary according to each individually negotiated license, the
Company's typical content license arrangement for its Proofing Tools calls for a
nonexclusive grant of rights for its use of the content in products it builds
for license to OEM customers. Content licenses for Information Products may be
made either on an exclusive or a nonexclusive basis. This usually includes the
right to refine and augment the content editorially for its purposes and the
right to use any associated trademarks and copyrights in the marketing of the
material both to and by licensees. The typical term of nonexclusive licenses is
five to 10 years.
 
EMPLOYEES
 
     As of August 31, 1996, the Company had 388 employees, including 203 in
research and development, 133 in sales and marketing, and 52 in financial and
administrative positions.
 
     The Company believes that its future success will depend in large part upon
its continued ability to recruit and retain highly qualified technical,
managerial, and marketing personnel. To date, the Company has been successful in
attracting and retaining skilled employees. None of the Company's employees is
represented by a labor union, and the Company considers its relationship with
its employees to be satisfactory.
 
                       RELATIONSHIP WITH HOUGHTON MIFFLIN
 
     In connection with the Company's IPO, the Company issued to Houghton
Mifflin 2,330 shares of its Series A Convertible Preferred Stock (the "Series A
Preferred Stock") in exchange for the assets and properties formerly
constituting the Software Division of Houghton Mifflin. The Series A Preferred
Stock converted into 4,660,000 shares of Common Stock, or approximately 40.3% of
the then outstanding shares of Common Stock, immediately following the issuance
of the Common Stock offered to the public in connection with the IPO.
Immediately following the issuance and sale of the 1,200,000 shares of Common
Stock being offered hereby by the Company, Houghton Mifflin will continue to
hold 4,015,100 shares of Common Stock, representing approximately 28.1% of the
outstanding shares of Common Stock.
 
     In August 1995, Houghton Mifflin completed a public offering of its SAILS.
Pursuant to the terms of the SAILS, Houghton Mifflin may, at its option, deliver
shares of Common Stock of the Company held by Houghton Mifflin upon exchange of
the SAILS. The SAILS will mature on August 1, 1999, unless previously redeemed
by Houghton Mifflin on or after August 1, 1998. After maturity of the SAILS, and
assuming the issuance and sale of 1,200,000 shares of Common Stock being offered
hereby by the Company, (i) if Houghton Mifflin elects to deliver cash in
exchange for the SAILS, it could continue to hold up to 4,015,100 shares of
Common Stock, representing 28.1% of the Company's outstanding Common Stock or
(ii) if Houghton Mifflin elects to deliver Common Stock in exchange for the
SAILS, it could hold, depending on the maturity price of the SAILS, from 175,100
to 704,636 shares, representing approximately 1.2% to 4.9% of the Company's
outstanding Common Stock.
 
     On January 10, 1994, the Company and Houghton Mifflin entered into a
Formation Agreement pursuant to which the Company agreed to assume the
obligations and liabilities of Houghton Mifflin relating to the Software
Division, and granted Houghton Mifflin certain registration rights with respect
to the shares of Common Stock issued upon conversion of the Series A Preferred
Stock held
 
                                       27
<PAGE>   28
 
by Houghton Mifflin. Under the Formation Agreement as amended to date, Houghton
Mifflin will be entitled to participate in certain registrations initiated by
the Company, at the Company's expense and subject to limitations that may be
imposed by the underwriters in an underwritten offering, during the three-year
period commencing on August 2, 1998. In addition, for a period of 180 days
following August 2, 1998, Houghton Mifflin will be entitled, on one occasion, to
request that the Company register for resale shares of Common Stock held by
Houghton Mifflin provided that (i) prior to August 2, 1998, either the Company
has not initiated a registration in which Houghton Mifflin could participate or,
if such a registration occurred, Houghton Mifflin was unable to register all of
the shares of Common Stock that Houghton Mifflin requested to be included
because of limitations imposed by the Company or its underwriters; and (ii) the
number of shares of Common Stock that Houghton Mifflin requests to be registered
has a market value at the date of such request of not less than $10,000,000.
 
     The Formation Agreement also provides that the Company will use its best
efforts to cause its Board to nominate persons selected by Houghton Mifflin for
election as directors of the Company so that two Houghton Mifflin nominees will
serve on the Board (or at least two-sevenths of the Board, if the size of the
Board is increased), so long as Houghton Mifflin holds at least 20% of the
Company's outstanding Common Stock. Originally, the two Houghton Mifflin
nominees on the Company's Board were William J. Wisneski, an executive officer
of Houghton Mifflin, and Stephen O. Jaeger, who resigned as Chief Financial
Officer of Houghton Mifflin effective as of March 15, 1995 and, until the
expiration of his term on April 26, 1995, was a member of Houghton Mifflin's
Board of Directors. The Company and Houghton Mifflin have agreed that Mr. Jaeger
will no longer be considered a Houghton Mifflin nominee and Houghton Mifflin
will have the right to nominate another person for election as a director of the
Company in accordance with the Formation Agreement. Houghton Mifflin has not
exercised this right at the present time. Another director of the Company, Mr.
Joseph A. Baute, is a director of Houghton Mifflin, but was not designated by
Houghton Mifflin for election to the Company's Board.
 
                                       28
<PAGE>   29
 
                                   MANAGEMENT
 
     The executive officers and directors of the Company are as follows:
 
<TABLE>
<CAPTION>
              NAME                 AGE                          POSITION
- ---------------------------------  ---     ---------------------------------------------------
<S>                                <C>     <C>
Steven R. Vana-Paxhia............   49     President, Chief Executive Officer, and Director
Kirby A. Mansfield...............   42     Vice President of Business Development
Jeffrey J. Melvin................   36     Vice President and General Manager of Tools and
                                           Technologies
Michael E. Melody................   52     Vice President and General Manager of Information
                                           Products
Carol J. Mitchell................   50     Vice President of Sales
Sunanda Mathai...................   45     Vice President of Engineering
Paul F. Henderson................   39     Vice President of Marketing
Betty J. Savage..................   38     Vice President, Chief Financial Officer, and
                                           Treasurer
Linda J. Barnes..................   38     Vice President and Controller
Bruce G. Hill....................   33     Vice President, General Counsel, and Secretary
J.P. Barger(1)(2)................   69     Director
Joseph A. Baute(2)(3)............   68     Director
Samuel H. Fuller(4)..............   50     Director
John Guttag(4)...................   47     Director
Stephen O. Jaeger(1).............   52     Director
Joanna T. Lau(1).................   38     Director
Raymond Stata(2)(3)..............   61     Director
William J. Wisneski(3)...........   50     Director
</TABLE>
 
- ---------------
(1) Member of the Audit Committee.
(2) Member of the Governance Committee.
(3) Member of the Compensation Committee.
(4) Member of the Technology and Strategy Committee.
 
     Steven R. Vana-Paxhia has been President and Chief Executive Officer and a
director of the Company since its inception on November 10, 1993. Mr.
Vana-Paxhia was Director of the Software Division of Houghton Mifflin from
November 1990 until March 1994 and was a Vice President of Houghton Mifflin from
April 1991 until March 1994. Prior to joining Houghton Mifflin, Mr. Vana-Paxhia
was Managing Director of Macmillan's Berlitz Translation Services from November
1987 until April 1990. Mr. Vana-Paxhia is also a director of Spyglass, Inc., a
provider of enabling technologies for the World Wide Web and MathSoft, Inc., a
software company.
 
     Kirby A. Mansfield has been Vice President of Business Development of the
Company since June 1994. From the inception of the Company until June 1994, Mr.
Mansfield was Vice President of Marketing and Business Development. Mr.
Mansfield joined Houghton Mifflin in July 1989 initially as a consultant for the
Software Division and subsequently as its Director of Technical Development. Mr.
Mansfield was appointed a Vice President of the Software Division in February
1992 and became Vice President and Director of Marketing and Business
Development of the Software Division in October 1993.
 
     Jeffrey J. Melvin has been Vice President and General Manager of Tools and
Technologies of the Company since October 1995. From January 1995 to October
1995, Mr. Melvin was Vice President of Sales and Marketing of the Company and
from the Company's inception to January 1995, he was the Company's Vice
President and Director of Sales. Mr. Melvin joined Houghton Mifflin in April
1991 as Director of Sales for the Software Division and was appointed Vice
President, Director of Sales of the Software Division in March 1993. Prior to
joining Houghton Mifflin, Mr. Melvin held various positions with Digital
Equipment Corporation ("DEC") beginning in 1983.
 
                                       29
<PAGE>   30
 
     Michael E. Melody has been Vice President and General Manager of
Information Products of the Company since March 1996. From October 1994 through
February 1996, Mr. Melody was Principal of Michael E. Melody, Consulting. From
October 1990 through September 1994, Mr. Melody was Executive Vice President,
College and Software Publishing of Houghton Mifflin. Prior to joining Houghton
Mifflin, Mr. Melody held various executive positions with Simon & Schuster,
Macmillan Publishing Company, and Prentice-Hall, Inc.
 
     Carol J. Mitchell has been Vice President of Sales of the Company since
October 1995 and was Director of OEM Sales of the Company from January 1995
until October 1995. Prior to joining the Company, Ms. Mitchell held various
sales management positions, including New England large account sales manager,
with DEC, beginning in 1986. Prior to joining DEC, Ms. Mitchell held various
sales and sales management positions with Wang Laboratories, beginning in 1978.
 
     Sunanda Mathai has been Vice President of Engineering of the Company since
its inception. Ms. Mathai joined Houghton Mifflin in October 1993 as the Vice
President of Engineering of the Software Division. Prior to joining Houghton
Mifflin, Ms. Mathai held several positions at ATEX, Inc., including Director of
Quality Assurance from March 1990 until September 1991 and Senior Director of
Engineering from October 1991 until joining Houghton Mifflin.
 
     Paul F. Henderson has been Vice President of Marketing of the Company since
August 1996. Prior to joining the Company, Mr. Henderson was Vice President of
Marketing of Centerline Software, Inc. from February 1995 until August 1996.
Prior to that time, Mr. Henderson held various positions at Sun Microsystems,
Inc., including Director of Marketing, Worldwide Field Operations, for SunSoft,
the software products business of Sun Microsystems, from June 1994 to January
1995.
 
     Betty J. Savage has been Vice President, Chief Financial Officer, and
Treasurer of the Company since its inception. Prior to joining the Company, Ms.
Savage had been employed with Ernst & Young LLP in auditing and other capacities
since 1980.
 
     Linda J. Barnes has been Vice President and Controller of the Company since
its inception. Ms. Barnes joined Houghton Mifflin in 1982 and became a Software
Division Vice President in March 1993.
 
     Bruce G. Hill has been Vice President, General Counsel, and Secretary of
the Company since March 1994. Prior to joining the Company, Mr. Hill had been an
associate attorney specializing in corporate and mergers and acquisitions
matters at the law firm of Skadden, Arps, Slate, Meagher & Flom in Boston,
Massachusetts, from 1988 until March 1994.
 
     J.P. Barger has been a director of the Company since March 8, 1994. Mr.
Barger, who is retired, was the Chairman of the Board of Dynatech Corporation, a
diversified manufacturer, from July 1991 until August 1994 and was its President
from 1959 until July 1991 and its Chief Executive Officer from 1987 until
January 1993.
 
     Joseph A. Baute has served as a director of the Company since its
inception. Mr. Baute has been a principal in Baute & Baute, a consulting firm
for family businesses, since 1993. Mr. Baute was Chairman and Chief Executive
Officer of Markem Corporation, which provides systems, supplies, and services to
mark customers' products, from 1979 until his retirement in June 1993. Mr. Baute
is also a director of Houghton Mifflin, Dead River Group, Nashua Corporation,
State Street Bank and Trust Company, and the Rodney Hunt Company and a member of
the Board of Advisors of Kearsage Capital Fund, L.P.
 
     Samuel H. Fuller has been a director of the Company since May 1996. Dr.
Fuller is currently Vice President, Corporate Technology Strategy and Chief
Scientist for DEC. Dr. Fuller has held various other positions with DEC since
1978, and served as its Vice President of Research from 1983 to January, 1996.
Dr. Fuller is also a director of Analog Devices, MCC and the National Research
Initiatives.
 
                                       30
<PAGE>   31
 
     John Guttag has been a director of the Company since May 1996. Dr. Guttag
is currently Associate Department Head for Computer Science of the Electrical
Engineering and Computer Science Department at the Massachusetts Institute of
Technology, where he has been a member of the faculty since 1979. Dr. Guttag is
also a director of Revco D.S. and of the Computing Research Association.
 
     Stephen O. Jaeger has been a director of the Company since its inception.
Since March 15, 1995, Mr. Jaeger has served as Vice President, Finance and Chief
Financial Officer of The Perkin-Elmer Corporation, a leading worldwide producer
of analytical instruments and life science systems. Mr. Jaeger was Chief
Financial Officer of Houghton Mifflin from 1988 until March 1995. Mr. Jaeger was
originally designated to serve as a director of the Company by Houghton Mifflin
under the Formation Agreement with Houghton Mifflin, but no longer serves in
such capacity.
 
     Joanna T. Lau has been a director of the Company since March 8, 1994. Ms.
Lau has been the President and Chairman of the Board of Lau Technologies, Inc.,
which provides manufacturing services for electronic systems and produces
digitized imaging identification systems, since March 1990. Ms. Lau held various
management positions at DEC and General Electric Company from 1981 until 1990.
Ms. Lau is also a director of FSI International, a semiconductor manufacturer.
 
     Raymond Stata has been a director of the Company since March 8, 1994. Mr.
Stata has been the Chairman of the Board and Chief Executive Officer of Analog
Devices, Inc., a manufacturer of hardware components for computer systems, since
1973 and was its President from 1971 until 1991.
 
     William J. Wisneski has been a director of the Company since its inception.
Mr. Wisneski has been Executive Vice President, School Publishing of Houghton
Mifflin since August 1992 and has held various other positions with Houghton
Mifflin and its subsidiaries since June 1990. Mr. Wisneski was President of
Learned & Tested, The Education Company, a supplementary materials subsidiary of
Harcourt Brace Jovanovich, Inc., from September 1988 until June 1990. Mr.
Wisneski was originally designated to serve as a director by Houghton Mifflin
under the Formation Agreement and continues to serve in such capacity.
 
                                       31
<PAGE>   32
 
                                  UNDERWRITING
 
     Subject to the terms and conditions of the Underwriting Agreement, Alex.
Brown & Sons Incorporated, Adams, Harkness & Hill, Inc., and Montgomery
Securities (the "Underwriters") have severally agreed to purchase from the
Company the following respective numbers of shares of Common Stock at the public
offering price less the underwriting discounts and commissions set forth on the
cover page of this Prospectus:
 
<TABLE>
<CAPTION>
                                                                                NUMBER
               UNDERWRITER                                                     OF SHARES
               -----------                                                     ---------
    <S>                                                                        <C>
    Alex. Brown & Sons Incorporated..........................................
    Adams, Harkness & Hill, Inc..............................................
    Montgomery Securities....................................................
                                                                               ---------
              Total..........................................................  1,200,000
                                                                               =========
</TABLE>
 
     The Underwriting Agreement provides that the obligations of the
Underwriters are subject to certain conditions precedent and that the
Underwriters will purchase all shares of the Common Stock offered hereby if any
such shares are purchased.
 
     The Company has been advised by the Underwriters that the Underwriters
propose to offer the shares of Common Stock to the public at the public offering
price set forth on the cover page of this Prospectus, and to certain dealers at
such price less a concession not in excess of $          per share. The
Underwriters may allow, and such dealers may reallow, a concession not in excess
of $          per share to certain other dealers. After the public offering, the
public offering price and other selling terms may be changed by the
Underwriters.
 
     The Company has granted to the Underwriters an option, exercisable not
later than 30 days after the date of this Prospectus, to purchase up to 180,000
additional shares of Common Stock at the public offering price less the
underwriting discounts and commissions set forth on the cover page of this
Prospectus. To the extent that the Underwriters exercise such option, each of
the Underwriters will have a firm commitment to purchase approximately the same
percentage thereof that the number of shares of Common Stock to be purchased by
it shown in the above table bears to 1,200,000 and the Company will be
obligated, pursuant to the option, to sell such shares to the Underwriters. The
Underwriters may exercise such option only to cover over-allotments made in
connection with the sale of the Common Stock offered hereby. If purchased, the
Underwriters will offer such additional shares on the same terms as those on
which the 1,200,000 shares are being offered.
 
     The Underwriting Agreement contains covenants of indemnity among the
Underwriters and the Company against certain civil liabilities, including
liabilities under the Securities Act.
 
     The Company, all executive officers and directors of the Company, and
Houghton Mifflin have agreed, subject to certain exceptions, not to offer, sell
or otherwise dispose of any shares of Common Stock for a period of 90 days after
the date of this Prospectus without the prior written consent of Alex. Brown &
Sons Incorporated, except that the Company may issue, and grant options to
purchase, shares of Common Stock under its current stock option and purchase
plans and other currently outstanding options and except that Houghton Mifflin
may sell up to 75,000 shares of Common Stock in open market transactions,
subject to certain other restrictions. In addition, the Company may issue shares
of Common Stock in connection with any acquisition of another company if the
terms of such issuance provide that such Common Stock shall not be resold prior
to the expiration of the 90-day period referenced in the preceding sentence.
 
     Certain of the Underwriters and selling group members (if any) that
currently act as market makers for the Common Stock may engage in "passive
market making" in the Common Stock on the Nasdaq National Market ("Nasdaq") in
accordance with Rule 10b-6A under the Securities Exchange Act of 1934, as
amended (the "Exchange Act"). Rule 10b-6A permits, upon the satisfaction of
 
                                       32
<PAGE>   33
 
certain conditions, underwriters and selling group members participating in a
distribution that are also Nasdaq market makers in the security being
distributed to engage in limited market making transactions during the period
when Rule 10b-6 under the Exchange Act would otherwise prohibit such activity.
Rule 10b-6A prohibits underwriters and selling group members engaged in passive
market making generally from entering a bid or effecting a purchase at a price
that exceeds the highest bid for those securities displayed on Nasdaq by a
market maker that is not participating in the distribution. Under Rule 10b-6A,
each underwriter or selling group member engaged in passive market making is
subject to a daily net purchase limitation equal to 30% of such entity's average
daily trading volume during the two full consecutive calendar months immediately
preceding the date of the filing of the registration statement under the
Securities Act pertaining to the security to be distributed. Passive market
making may stabilize the market price of the Common Stock at a level above that
which might otherwise prevail and, if commenced, may be discontinued at any
time.
 
     Alex. Brown & Sons Incorporated provided financial advisory services to the
Company in connection with the Company's acquisition of EBT on July 16, 1996.
 
                                 LEGAL MATTERS
 
     Certain legal matters will be passed upon for the Company by Hale and Dorr,
Boston, Massachusetts. Certain legal matters in connection with the offering
will be passed upon for the Underwriters by Skadden, Arps, Slate, Meagher &
Flom, Boston, Massachusetts.
 
                                    EXPERTS
 
     The consolidated financial statements (including schedules incorporated by
reference) of INSO Corporation at December 31, 1995 and 1994, and for each of
the three years in the period ended December 31, 1995, appearing in this
Prospectus and Registration Statement have been audited by Ernst & Young LLP,
independent auditors, as set forth in their reports thereon appearing and
incorporated by reference herein. The consolidated financial statements of
Electronic Book Technologies, Inc. at December 31, 1995 and 1994 and for the
years then ended appearing in INSO Corporation's Report on Form 8-K/A filed
September 17, 1996 have been audited by Ernst & Young LLP, as set forth in their
report included therein and incorporated herein by reference. The consolidated
financial statements referred to above are included and incorporated herein by
reference in reliance upon such reports given upon the authority of such firm as
experts in accounting and auditing.
 
                                       33
<PAGE>   34
 
                             AVAILABLE INFORMATION
 
     The Company is subject to the informational requirements of the Exchange
Act and in accordance with the Exchange Act files reports, proxy statements and
other information with the Securities and Exchange Commission (the "SEC"). The
Company has filed a registration statement on Form S-3 (the "Registration
Statement") under the Securities Act with the SEC with respect to the Common
Stock offered hereby. This Prospectus, which constitutes part of the
Registration Statement, does not contain all the information set forth in the
Registration Statement and reference is made to the Registration Statement and
the exhibits thereto for further information with respect to the Company and the
Common Stock. Such reports, proxy statements, Registration Statement and
exhibits and other information omitted from this Prospectus can be inspected and
copied at the public reference facilities maintained by the SEC at 450 Fifth
Street, N.W., Room 1024, Washington, D.C. 20549 and at the SEC's Regional
Offices located at Seven World Trade Center, Suite 1300, New York, N.Y. 10048
and Citicorp Center, 500 West Madison Street, Suite 1400, Chicago, IL
60661-2511. Copies of such material can be obtained at prescribed rates from the
Public Reference Section of the SEC, 450 Fifth Street, N.W., Room 1024,
Washington, D.C. 20549. Such reports, proxy statements and other information
concerning the Company can be inspected at the Nasdaq Stock Market at 1735 K
Street, N.W., Washington, D.C. 20006. In addition, the Company is required to
file electronic versions of these documents with the SEC through the SEC's
Electronic Data Gathering, Analysis, and Retrieval (EDGAR) system. The SEC
maintains a World Wide Web site at http://www.sec.gov that contains reports,
proxy and information statements and other information regarding registrants
that file electronically with the SEC.
 
                INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE
 
     The Company's Annual Report on Form 10-K for the fiscal year ended December
31, 1995, the Company's Quarterly Reports on Form 10-Q for the quarters ended
March 31, 1996 and June 30, 1996, the Company's Current Report on Form 8-K dated
July 16, 1996, including the amendment thereto on Form 8-K/A filed with the SEC
on September 17, 1996, and the description of the Common Stock contained in the
Company's Registration Statement on Form 8-A filed by the Company with the SEC
on February 2, 1994, are incorporated by reference in this Prospectus. All
documents filed by the Company pursuant to Sections 13(a), 13(c), 14, or 15(d)
of the Exchange Act subsequent to the date of this Prospectus and prior to the
termination of the offering made hereby shall be deemed to be incorporated by
reference into this Prospectus and to be made a part hereof from the respective
dates of filing of such documents. Any statement in any document incorporated or
deemed to be incorporated by reference herein shall be deemed to be modified or
superseded for purposes of the Registration Statement and this Prospectus to the
extent that a statement contained herein or in any subsequently filed document
which also is or is deemed to be incorporated by reference herein modifies or
supersedes such statement. Any such statement so modified or superseded shall
not be deemed, except as so modified or superseded, to constitute a part of the
Registration Statement or this Prospectus.
 
     Copies of the above documents (other than exhibits to such documents unless
such exhibits are specifically incorporated by reference in such documents) may
be obtained upon written or oral request without charge from the Company, 31 St.
James Avenue, Boston, MA 02116-4101, Attention: Investor Relations, telephone
(617) 753-6500.
 
                                       34
<PAGE>   35
 
                   INDEX TO CONSOLIDATED FINANCIAL STATEMENTS
 
<TABLE>
<CAPTION>
                                                                                        PAGE
                                                                                        ----
<S>                                                                                     <C>
Report of Independent Auditors........................................................   F-2
Consolidated Balance Sheets at December 31, 1995 and 1994.............................   F-3
Consolidated Statements of Income for the years ended December 31, 1995, 1994, and
  1993................................................................................   F-4
Consolidated Statements of Cash Flows for the years ended December 31, 1995, 1994, and
  1993................................................................................   F-5
Consolidated Statement of Stockholders' Equity for the years ended December 31, 1995
  and 1994............................................................................   F-6
Notes to Consolidated Financial Statements............................................   F-7
Pro Forma Consolidated Financial Information (Unaudited)..............................  F-17
</TABLE>
 
                                       F-1
<PAGE>   36
 
                         REPORT OF INDEPENDENT AUDITORS
 
The Board of Directors and Stockholders
INSO Corporation
 
     We have audited the accompanying consolidated balance sheets of INSO
Corporation as of December 31, 1995 and 1994, the related consolidated
statements of income and cash flows for each of the three years in the period
ended December 31, 1995, and the related consolidated statements of
stockholders' equity for each of the two years in the period ended December 31,
1995. These financial statements are the responsibility of the Company's
management. Our responsibility is to express an opinion on these financial
statements based on our audits.
 
     We conducted our audits in accordance with generally accepted auditing
standards. Those standards require that we plan and perform the audit to obtain
reasonable assurance about whether the financial statements are free of material
misstatement. An audit includes examining, on a test basis, evidence supporting
the amounts and disclosures in the financial statements. An audit also includes
assessing the accounting principles used and significant estimates made by
management, as well as evaluating the overall financial statement presentation.
We believe that our audits provide a reasonable basis for our opinion.
 
     In our opinion, the consolidated financial statements referred to above
present fairly, in all material respects, the consolidated financial position of
INSO Corporation at December 31, 1995 and 1994, and the consolidated results of
its operations and its cash flows for each of the three years in the period
ended December 31, 1995, in conformity with generally accepted accounting
principles.
 
                                          ERNST & YOUNG LLP
Boston, Massachusetts
February 1, 1996
 
                                       F-2
<PAGE>   37
 
                                INSO CORPORATION
 
                          CONSOLIDATED BALANCE SHEETS
                           DECEMBER 31, 1995 AND 1994
 
<TABLE>
<CAPTION>
                                                                       YEAR ENDED
                                                                      DECEMBER 31,
                                                                   -------------------
                                                                    1995        1994
                                                                   -------     -------
                                                                      (IN THOUSANDS
                                                                      EXCEPT SHARE
                                                                        AMOUNTS)
<S>                                                                <C>         <C>
                                        ASSETS
Current assets:
  Cash and cash equivalents......................................  $37,235     $13,858
  Marketable securities..........................................   25,397
  Accounts receivable, net of allowances of $790 in 1995 and $372
     in 1994.....................................................    8,264       7,464
  Other current assets...........................................      530          80
                                                                   -------     -------
          Total current assets...................................   71,426      21,402
Property and equipment, at cost:
  Leasehold improvements.........................................      476          18
  Computer equipment and software................................    3,880       2,189
  Furniture and fixtures.........................................      711          78
                                                                   -------     -------
                                                                     5,067       2,285
Less accumulated amortization and depreciation...................   (2,810)     (1,313)
                                                                   -------     -------
                                                                     2,257         972
Royalty advances and other assets, net...........................      980       1,094
Product development costs, net of accumulated amortization of
  $6,775 in 1995 and $4,734 in 1994..............................    3,229       2,156
Intangible assets, net of accumulated amortization of $1,491 in
  1995 and $328 in 1994..........................................    9,390       3,695
Deferred income tax benefit, net.................................    3,847       4,175
                                                                   -------     -------
          Total Assets...........................................  $91,129     $33,494
                                                                   =======     =======
                         LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities:
  Accounts payable and accrued liabilities.......................  $ 1,885     $   787
  Accrued salaries, commissions, and bonuses.....................    2,094       1,272
  Unearned revenue...............................................      875         375
  Royalties payable..............................................    1,461       1,212
  Due to Houghton Mifflin Company................................      314         903
  Promissory notes...............................................    6,037
  Current income taxes payable...................................      883          61
  Deferred income taxes..........................................    2,417       1,270
                                                                   -------     -------
          Total current liabilities..............................   15,966       5,880
Commitments and contingencies
Stockholders' equity:
  Preferred stock, $.01 par value; 1,000,000 shares authorized;
     none issued.................................................
  Common stock, $.01 par value; 25,000,000 and 12,000,000 shares
     authorized in 1995 and 1994, respectively; 12,965,700 and
     5,814,211 shares issued in 1995 and 1994, respectively......      130          58
  Capital in excess of par value.................................   64,096      22,420
  Retained earnings..............................................   11,657       5,663
                                                                   -------     -------
                                                                    75,883      28,141
  Unamortized value of restricted shares.........................     (669)       (506)
  Treasury stock, at cost, 4,975 and 850 shares in 1995 and 1994,
     respectively................................................      (51)        (21)
                                                                   -------     -------
          Total stockholders' equity.............................   75,163      27,614
                                                                   -------     -------
          Total Liabilities and Stockholders' Equity.............  $91,129     $33,494
                                                                   =======     =======
</TABLE>
 
          See accompanying Notes to Consolidated Financial Statements.
 
                                       F-3
<PAGE>   38
 
                                INSO CORPORATION
 
                       CONSOLIDATED STATEMENTS OF INCOME
 
<TABLE>
<CAPTION>
                                                                    YEAR ENDED DECEMBER 31,
                                                                  ---------------------------
                                                                   1995      1994      1993
                                                                  -------   -------   -------
                                                                   (IN THOUSANDS EXCEPT PER
                                                                        SHARE AMOUNTS)
<S>                                                               <C>       <C>       <C>
Net revenues....................................................  $43,387   $23,463   $13,757
Cost of revenues................................................    5,792     3,074     1,870
                                                                  -------   -------   -------
  Gross profit..................................................   37,595    20,389    11,887
Operating expenses:
  Sales and marketing...........................................    6,570     3,676     2,612
  Product development...........................................    7,489     4,728     2,932
  General and administrative....................................    6,458     3,452     1,957
  Purchased in-process research and development.................    5,500
                                                                  -------   -------   -------
          Total operating expenses..............................   26,017    11,856     7,501
                                                                  -------   -------   -------
Operating income................................................   11,578     8,533     4,386
Net investment income...........................................    1,468       319
                                                                  -------   -------   -------
Income before provision for income taxes........................   13,046     8,852     4,386
Income tax expense..............................................    7,052     3,189     1,811
                                                                  -------   -------   -------
Net income......................................................  $ 5,994   $ 5,663   $ 2,575
                                                                  =======   =======   =======
Primary earnings per share......................................  $  0.49   $  0.48   $  0.22
                                                                  =======   =======   =======
Fully diluted earnings per share................................  $  0.47   $  0.47   $  0.22
                                                                  =======   =======   =======
</TABLE>
 
          See accompanying Notes to Consolidated Financial Statements.
 
                                       F-4
<PAGE>   39
 
                                INSO CORPORATION
 
                     CONSOLIDATED STATEMENTS OF CASH FLOWS
 
<TABLE>
<CAPTION>
                                                                         YEAR ENDED
                                                                        DECEMBER 31,
                                                                -----------------------------
                                                                  1995       1994      1993
                                                                --------   --------   -------
                                                                  (IN THOUSANDS OF DOLLARS)
<S>                                                             <C>        <C>        <C>
Cash flows from (used in) operating activities:
  Net income..................................................  $  5,994   $  5,663   $ 2,575
  Adjustments to reconcile net income to net cash provided by
     operating activities:
     Depreciation and amortization............................     3,712      1,504       464
     Purchased in-process research and development............     5,500
                                                                --------   --------   -------
                                                                  15,206      7,167     3,039
  Changes in operating assets and liabilities:
     Accounts receivable......................................       189     (3,226)   (2,451)
     Royalty advances.........................................       414       (779)      (27)
     Accounts payable and accrued liabilities.................     1,861      1,941        93
     Current and deferred income taxes........................     2,495        789       378
     Royalties payable........................................       266        310       372
     Due to Houghton Mifflin Company..........................      (589)       773
     Other assets and liabilities.............................      (122)      (123)
                                                                --------   --------   -------
     Net cash provided by operating activities................    19,720      6,852     1,404
Cash flows from (used in) investing activities:
  Property and equipment expenditures.........................    (2,211)    (1,040)     (225)
  Capitalized product development costs.......................    (1,364)    (1,352)     (806)
  Acquisition of Systems Compatibility Corporation, net of
     cash acquired and issuance of promissory notes...........    (4,184)
  Purchase of rights of Information Please(R) Almanacs........    (3,455)
  Purchase of marketable securities...........................   (25,397)
  Software license............................................               (4,023)
                                                                --------   --------   -------
     Net cash used in investing activities....................   (36,611)    (6,415)   (1,031)
Cash flows from (used in) financing activities:
  Net proceeds from issuance of common stock..................    39,616     47,399
  Payment to Houghton Mifflin Company and transfer of net
     assets...................................................              (34,155)
  Principal stockholder's contribution to capital.............                  130
  Purchases of treasury stock.................................       (30)       (21)
  Proceeds from exercise of stock options.....................     1,012         68
  Repayment of promissory notes...............................      (330)
                                                                --------   --------   -------
     Net cash provided by financing activities................    40,268     13,421
                                                                --------   --------   -------
Net increase in cash and cash equivalents.....................    23,377     13,858
Net cash transferred to Houghton Mifflin
  Company.....................................................                        $   373
                                                                                      =======
Cash and cash equivalents at beginning of the period..........    13,858          0   $     0
                                                                --------   --------   -------
Cash and cash equivalents at end of the period................  $ 37,235   $ 13,858   $     0
                                                                ========   ========   =======
Supplementary information:
  Income taxes paid...........................................  $  5,017   $  2,312
                                                                ========   ========
</TABLE>
 
          See accompanying Notes to Consolidated Financial Statements.
 
                                       F-5
<PAGE>   40
 
                                INSO CORPORATION
 
                CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY
                     YEARS ENDED DECEMBER 31, 1995 AND 1994
 
<TABLE>
<CAPTION>
                                 COMMON STOCK
                         ----------------------------   CAPITAL IN                  UNAMORTIZED
                                          AMOUNT         EXCESS OF    RETAINED        VALUE OF        TREASURY   STOCK
                           SHARES     $.01 PAR VALUE     PAR VALUE    EARNINGS   RESTRICTED SHARES     SHARES    AMOUNT    TOTAL
                         ----------   ---------------   -----------   --------   ------------------   --------   ------   -------
                                                           (IN THOUSANDS EXCEPT SHARE AMOUNTS)
<S>                      <C>          <C>               <C>           <C>        <C>                  <C>        <C>      <C>
BALANCE AT JANUARY 1,
  1994.................                                                                                                   $     0
Net proceeds from
  initial public
  offering.............   3,450,000        $  35         $  47,262                                                         47,297
Payment to Houghton
  Mifflin Company and
  transfer of net
  assets...............   2,321,300           23           (31,029)                                                       (31,006)
Deferred income tax
  benefit,
  net..................                                      5,326                                                          5,326
Stock options
  exercised............       4,500                            100                                                            100
Issuance of restricted
  shares...............      23,518                            552                     $ (552)                                  0
Principal stockholder's
  contribution to
  capital..............       8,700                            130                                                            130
Issuance of shares
  pursuant to
  Employee Stock
  Purchase
  Plan.................       6,193                             79                                                             79
Share repurchases......                                                                                   850     $(21)       (21)
Amortization of
  restricted shares....                                                                    46                                  46
Net income.............                                               $ 5,663                                               5,663
                         ----------         ----          --------    -------           -----           -----     ----    -------
BALANCE AT DECEMBER 31,
  1994.................   5,814,211        $  58         $  22,420    $ 5,663          $ (506)            850     $(21)   $27,614
Issuance of shares
  pursuant to
  Employee Stock
  Purchase Plan
  and Benefit Plan.....      18,414                            501                                                            501
Net proceeds from
  public
  offering.............     600,000            6            39,286                                                         39,292
Stock options
  exercised............      45,875            1             1,011                                                          1,012
Issuance of restricted
  shares...............      10,500                            336                       (336)                                  0
Other issuances and
  repurchases..........       3,500                            119                                      4,125      (30)        89
Two-for-one stock
  split................   6,473,200           65               (65)                                                             0
Amortization of
  restricted
  shares...............                                                                   173                                 173
Tax benefits of stock
  option
  exercises............                                        488                                                            488
Net income.............                                                 5,994                                               5,994
                         ----------         ----          --------    -------           -----           -----     ----    -------
BALANCE AT DECEMBER 31,
  1995.................  12,965,700        $ 130         $  64,096    $11,657          $ (669)          4,975     $(51)   $75,163
                         ==========         ====          ========    =======           =====           =====     ====    =======
</TABLE>
 
          See accompanying Notes to Consolidated Financial Statements.
 
                                       F-6
<PAGE>   41
 
                                INSO CORPORATION
 
                   NOTES TO CONSOLIDATED FINANCIAL STATEMENTS
 
NOTE 1.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
 
Basis of Presentation
 
     INSO Corporation, formerly InfoSoft International, Inc., (the "Company")
was formed on November 10, 1993, as the successor Company to the Software
Division of Houghton Mifflin Company ("Houghton Mifflin"). At the time of
incorporation in Delaware, the Board of Directors established a class of Series
A Convertible Preferred Stock with priority dividend rights (the "Series A
Preferred"). The Company and Houghton Mifflin entered into a Formation Agreement
on January 10, 1994, in which Houghton Mifflin agreed to purchase all of the
Company's authorized Series A Preferred and transfer to the Company the net
assets and business of the Software Division. The transactions provided for in
the Formation Agreement were consummated concurrent with the Company's
completion of an initial public offering of its common stock on March 8, 1994.
The shares of Series A Preferred issued to Houghton Mifflin were entitled to a
preferential dividend equal to 80% of the net proceeds received by the Company
in connection with the sale of the common stock in such public offering.
Simultaneous with the payment of the dividend, the Series A Preferred was
converted into 4,660,000 shares of common stock, equivalent to approximately a
40% equity interest in the Company.
 
     The accompanying financial statements are presented as though the Company
had existed as a corporation separate from Houghton Mifflin throughout the
periods presented and include the historical assets, liabilities, revenues, and
expenses that are directly related to the Company's operations, including
expenses charged to the Company by Houghton Mifflin. (See Notes 6 and 7.)
 
Nature of Operations
 
     The Company is a provider of multilingual software products that help
people enhance the quality of their written communications, provide them with
access to information from authoritative sources, and make it easier for them to
locate, retrieve, and view information, regardless of format or structure. The
Company markets its products worldwide to original equipment manufacturers
(OEMs) of computer hardware, software and consumer electronics products;
corporations; and end users. These operations are reported as one business
segment.
 
Principles of Consolidation
 
     The consolidated financial statements include the accounts of the Company
and its wholly owned subsidiaries. All significant intercompany accounts and
transactions have been eliminated.
 
Revenue Recognition
 
     The Company derives its revenues from royalties, including initial
nonrefundable royalties from license arrangements, one-time license and annual
software maintenance fees from site-license agreements with corporate customers,
and from one-time fees for direct licenses to customers. Royalty revenue is
earned in one of the following ways: as a percentage of net revenues from
product unit sales by licensees that incorporate the Company's products, as a
fixed per-unit royalty, or as a regular periodic fee based on estimated
shipments or usage over time.
 
     The Company accounts for revenue in accordance with Statement of Position
91-1, "Software Revenue Recognition," issued by the American Institute of
Certified Public Accountants. Specifically, royalty revenues are generally
recognized in the Company's financial statements in the quarter in which amounts
due to the Company have been determined. In the event that further substantial
support or performance obligations exist, revenue is recognized ratably as
earned. Revenues from initial nonrefundable royalty arrangements are recognized
at the time of product acceptance by the
 
                                       F-7
<PAGE>   42
 
                                INSO CORPORATION
 
           NOTES TO CONSOLIDATED FINANCIAL STATEMENTS -- (CONTINUED)
 
licensee if no significant obligation relating to the underlying contract
remains to be completed. Nonrefundable royalty amounts payable to the Company
according to specified payment dates are recorded as receivables. Revenues from
corporate site licenses are recognized at the time of the delivery to the
customer. Revenues for maintenance agreements are recognized as income over the
term of the agreement using the straight-line method.
 
Cash and Cash Equivalents
 
     The Company considers highly liquid investments with maturities of three
months or less at the time of purchase to be cash equivalents.
 
Investments
 
     The Company accounts for its investments in securities, including certain
cash equivalents and marketable securities, in accordance with Statement of
Financial Accounting Standards No. 115, "Accounting for Certain Investments in
Debt and Equity Securities." The appropriate classification of debt securities
is determined at the time of purchase and is reevaluated at each balance sheet
date. (See Note 2.)
 
Product Development Costs
 
     Software and other costs incurred in connection with product development
are charged to expense until such time as specific product technological
feasibility has been established. Thereafter, product development costs specific
to the product are capitalized and reported at the lower of unamortized cost or
net realizable value.
 
     Amortization of capitalized product development costs begins when the
related product is available for general release to customers. These costs are
amortized using the shorter of the estimated future product revenue streams or
the straight-line method over a period not exceeding three years.
 
     Amortization of $1,308,000, $588,000, and $245,000 for the years ended
1995, 1994, and 1993, respectively, are included as a component of cost of
revenues.
 
Royalty Advances
 
     Royalty advances, which pertain to payments by the Company for the license
of technology and/or content used in its products, are stated at cost less
royalty amounts expensed based on revenues recognized over the life of the
related agreement.
 
Property and Equipment
 
     Property and equipment are stated at cost. Depreciation is provided using
an accelerated method over the estimated economic life of the assets, generally
three to five years. Depreciation is provided on leasehold improvements using
the straight-line method over the economic life of the asset or the lease term,
whichever is shorter.
 
Intangible Assets
 
     Intangible assets are being amortized over their estimated economic lives.
If facts and circumstances suggest that an impairment may have occurred, the
unamortized balances of these assets are reviewed under the provisions of
Statement of Financial Accounting Standards No. 121 "Accounting for the
Impairment of Long-Lived Assets and for Long-Lived Assets to be Disposed of." If
this review
 
                                       F-8
<PAGE>   43
 
                                INSO CORPORATION
 
           NOTES TO CONSOLIDATED FINANCIAL STATEMENTS -- (CONTINUED)
 
indicates that the remaining balance is not recoverable, as determined based
upon the estimated undiscounted cash flows of the asset during its remaining
economic life, the value assigned to the asset would be reduced to its fair
value.
 
Concentration of Credit Risk
 
     In 1995, 1994, and 1993 one customer accounted for 52%, 55%, and 48% of
revenues, respectively. The 1995 revenues for that customer include $1,500,000
of non-recurring revenue earned from royalty audits. The Company performs
ongoing credit evaluations of its customers and maintains reserves for potential
credit losses; to date, losses have not been material to the Company's financial
position or results of operations.
 
     The Company licenses its products primarily to customers in North America.
Sales to foreign customers accounted for $5,673,000, $4,216,000, and $3,076,000
for the years ended December 31, 1995, 1994, and 1993, respectively.
Substantially all export sales have been consummated by the Company's United
States operation.
 
Stock-Based Compensation
 
     The Company has elected to follow Accounting Principles Board Opinion No.
25, "Accounting for Stock Issued to Employees" (APB 25) and related
interpretations in accounting for its stock-based compensation plans rather than
the alternative fair value accounting provided under Statement of Financial
Accounting Standards No. 123, "Accounting for Stock-Based Compensation" (SFAS
123). The Company expects to continue to account for stock issued to employees
in accordance with APB 25 and will make all disclosures required by SFAS 123
beginning in fiscal year 1996.
 
Earnings Per Share
 
     As the Company's operations were included in the consolidated financial
statements of Houghton Mifflin on a divisional basis prior to the initial public
offering, there are no stockholder equity accounts for the Company prior to
1994. Common shares outstanding of 11,560,000 at March 8, 1994, have been
included in the earnings per share calculation as if the shares were outstanding
for all periods prior to March 8, 1994. Primary and fully diluted earnings per
share are based on the weighted average number of shares outstanding during the
period and the assumed exercise of dilutive stock options using the treasury
stock method. The primary weighted average number of common and equivalent
shares outstanding was 12,228,000 in 1995, 11,798,000 in 1994, and 11,560,000 in
1993. The fully diluted weighted average number of common and equivalent shares
outstanding was 12,839,000 in 1995, 11,946,000 in 1994, and 11,560,000 in 1993.
 
Use of Estimates
 
     The preparation of financial statements in conformity with generally
accepted accounting principles requires management to make estimates and
assumptions that affect the amounts reported in the financial statements and
accompanying notes. Actual results could differ from those estimates.
 
Reclassifications
 
     Certain reclassifications have been made to the prior year's consolidated
financial statements to conform to the 1995 presentation.
 
                                       F-9
<PAGE>   44
 
                                INSO CORPORATION
 
           NOTES TO CONSOLIDATED FINANCIAL STATEMENTS -- (CONTINUED)
 
NOTE 2.  INVESTMENTS
 
     The Company's available-for-sale investments carried at cost which
approximates fair value, included in cash equivalents and marketable securities,
are as follows:
 
<TABLE>
<CAPTION>
                                                                          YEAR ENDED
                                                                         DECEMBER 31,
                                                                       -----------------
                                                                        1995      1994
                                                                       -------   -------
                                                                       (IN THOUSANDS OF
                                                                           DOLLARS)
    <S>                                                                <C>       <C>
    Commercial paper.................................................  $26,950   $ 1,000
    Corporate notes..................................................    9,707
    Money market funds...............................................    9,697     6,300
    Tax-exempt municipal bonds.......................................  8,726..     6,050
    United States agency bonds.......................................    4,993
    Asset-backed securities..........................................    1,971
                                                                       -------   -------
              Total..................................................  $62,044   $13,350
                                                                       =======   =======
</TABLE>
 
     Interest on securities classified as available-for-sale of $1,208,000 and
$321,000 is included in net investment income in 1995 and 1994, respectively.
Dividend income, included in net investment income, for securities classified as
available-for-sale was $269,000 in 1995.
 
     At December 31, 1995, $50,366,000 of securities mature within one year and
$11,678,000 of securities mature between one and two years. At December 31,
1994, all securities were to mature within 90 days.
 
NOTE 3.  COMMON STOCK
 
     On August 2, 1995, the Company completed a public offering of 600,000
shares (1,200,000 shares adjusted for stock dividend) of the Company's common
stock, which provided the Company with net proceeds of approximately
$39,300,000.
 
     On September 1, 1995, the Company effected a two-for-one stock split in the
form of a stock dividend of one share of common stock for each outstanding share
of common stock. The dividend was payable to holders of record on August 18,
1995. All references in the financial statements to the average number of shares
outstanding and related prices, per share amounts, stock plans data, and benefit
plan data have been retroactively restated to reflect this transaction. In
addition, an amount equal to the par value of the shares outstanding at
September 1, 1995, has been transferred from capital in excess of par to common
stock.
 
NOTE 4.  ACQUISITIONS AND LICENSE AGREEMENTS
 
Systems Compatibility Corporation
 
     On April 1, 1995, the Company acquired all of the outstanding capital stock
of privately held Systems Compatibility Corporation (SCC), now INSO Chicago, for
a purchase price of $12,367,500. The purchase was paid in the form of $6,000,000
in cash and $6,367,500 in promissory notes with a final payment due on February
1, 1996. The notes were supported by outstanding letters of credit. The
transaction was accounted for as a purchase and has been included in the
consolidated financial statements since the date of acquisition. The acquisition
included the purchase of certain technology under research and development,
which resulted in a charge to the Company's consolidated results for the quarter
ended June 30, 1995, of $5,500,000, or $0.44 per share. The charge was not
deductible for tax purposes. The purchase price has been allocated on the basis
of the estimated fair market value of the assets acquired and liabilities
assumed. Intangible assets of $3,842,000 were
 
                                      F-10
<PAGE>   45
 
                                INSO CORPORATION
 
           NOTES TO CONSOLIDATED FINANCIAL STATEMENTS -- (CONTINUED)
 
recorded as part of the acquisition and are being amortized on a straight-line
basis over their estimated useful lives of seven years.
 
     Unaudited pro-forma revenue, net income, and earnings per share shown below
for the years ended December 31, 1995 and 1994 assume the acquisition occurred
on January 1, 1995 and 1994, respectively:
 
<TABLE>
<CAPTION>
                                                                    YEAR ENDED DECEMBER
                                                                            31,
                                                                   ---------------------
                                                                    1995          1994
                                                                   -------       -------
                                                                        (UNAUDITED)
                                                                     (IN THOUSANDS OF
                                                                          DOLLARS
                                                                     EXCEPT PER SHARE
                                                                         AMOUNTS)
    <S>                                                            <C>           <C>
    Revenue......................................................  $45,093       $29,285
    Net income...................................................  $ 5,819       $ 5,740
    Earnings per share...........................................  $  0.48       $  0.49
</TABLE>
 
Information Please(R) Almanacs
 
     On July 5, 1995, the Company acquired all rights to the Information
Please(R) names, trademarks, copyrights, and related assets from Houghton
Mifflin for approximately $3,600,000. Approximately $3,300,000 of the total
acquisition price was allocated to the aforementioned publishing rights and is
being amortized on a straight-line basis over an estimated useful life of 15
years as determined by the revenue history of the Information Please(R)
almanacs.
 
Microlytics, Inc.
 
     Effective March 3, 1994, the Company consummated a license agreement with
Microlytics, Inc. and its parent, SelecTronics, Inc., for rights to certain of
Microlytics' proofing tools and certain related products. In connection with
this license agreement, the Company was assigned certain license agreements
between Microlytics and its OEM customers. The initial term of the license
agreement is eight years with five, one-year renewal options. The net cost for
the license and assignment of contracts was $4,023,000 plus a royalty if annual
revenue from the licensed products exceeds certain amounts. The license is being
amortized over the initial eight-year period based on the relationship of
current period revenues to anticipated total revenues during the license period.
 
NOTE 5.  INCOME TAXES
 
     The taxable income of the Company was included in the consolidated tax
returns of Houghton Mifflin until the completion of the initial public offering
described in Note 1. Income tax expense has been provided as though the Company
were filing separate tax returns for all periods prior to the initial public
offering.
 
                                      F-11
<PAGE>   46
 
                                INSO CORPORATION
 
           NOTES TO CONSOLIDATED FINANCIAL STATEMENTS -- (CONTINUED)
 
     Income tax expense comprised the following:
 
<TABLE>
<CAPTION>
                                                                 YEAR ENDED DECEMBER 31,
                                                                 ------------------------
                                                                  1995     1994     1993
                                                                 ------   ------   ------
                                                                     (IN THOUSANDS OF
                                                                         DOLLARS)
    <S>                                                          <C>      <C>      <C>
    Current:
      Federal..................................................  $4,239   $1,818   $  963
      Foreign..................................................     230      190      176
      State....................................................   1,108      401      341
                                                                 ------   ------   ------
              Total current....................................   5,577    2,409    1,480
    Deferred:
      Federal..................................................   1,320      710      255
      State....................................................     155       70       76
                                                                 ------   ------   ------
              Total deferred...................................   1,475      780      331
                                                                 ------   ------   ------
                                                                 $7,052   $3,189   $1,811
                                                                 ======   ======   ======
</TABLE>
 
     A reconciliation of income tax expense to the statutory federal income tax
rate was as follows:
 
<TABLE>
<CAPTION>
                                                        YEAR ENDED DECEMBER 31,
                                           --------------------------------------------------
                                                1995              1994              1993
                                           --------------    --------------    --------------
                                                       (IN THOUSANDS OF DOLLARS)
    <S>                                    <C>      <C>      <C>      <C>      <C>      <C>
    Federal statutory rate................ $4,566   35.00%   $3,010   34.00%   $1,535   35.00%
    State income taxes, net of
      federal effect......................    775    5.94       311    3.51       272    6.19
    Change in valuation allowance.........   (328)  (2.51)     (302)  (3.41)
    Purchased in-process research and
      development.........................  1,925   14.75
    INSO Chicago intangible asset
      amortization........................    264    2.02
    Research and development credit.......   (294)  (2.25)      (26)   (.29)
    Other.................................    144    1.10       196    2.21         4    0.10
                                           ------   -----    ------   -----    ------   -----
              Total....................... $7,052   54.05%   $3,189   36.02%   $1,811   41.29%
                                           ======   =====    ======   =====    ======   =====
</TABLE>
 
     Significant components of the Company's net deferred income tax
assets/(liabilities) were as follows:
 
<TABLE>
<CAPTION>
                                                                YEAR ENDED DECEMBER 31,
                                                              ---------------------------
                                                               1995      1994      1993
                                                              -------   -------   -------
                                                               (IN THOUSANDS OF DOLLARS)
    <S>                                                       <C>       <C>       <C>
    Net deferred tax assets:
      Intangible assets.....................................  $ 9,456   $10,165
      Valuation allowance...................................   (4,808)   (5,135)
      Capitalized development costs.........................     (860)     (827)
      Deferred income.......................................     (193)     (193)
      Other.................................................      252       165
                                                              -------   -------
                                                                3,847     4,175
    Net deferred tax liabilities:
      Deferred income.......................................    2,883     1,511   $ 1,218
      Capitalized development costs.........................                          545
      Other.................................................     (466)     (241)     (150)
                                                              -------   -------   -------
                                                                2,417     1,270     1,613
                                                              -------   -------   -------
    Net deferred income tax assets/(liabilities)............  $ 1,430   $ 2,905   $(1,613)
                                                              =======   =======   =======
</TABLE>
 
                                      F-12
<PAGE>   47
 
                                INSO CORPORATION
 
           NOTES TO CONSOLIDATED FINANCIAL STATEMENTS -- (CONTINUED)
 
     The deferred income tax benefit included on the accompanying consolidated
balance sheet relates to a tax basis difference between assets for financial
reporting and for income tax purposes, primarily tax basis intangible assets
arising in connection with the formation of the Company and completion of the
initial public offering. The valuation allowance of $4,808,000 and $5,135,000 at
December 31, 1995 and 1994, respectively, was determined after evaluating the
Company's historical operating results and anticipated performance over its
normal planning horizon. The Company periodically evaluates the valuation
allowance and makes adjustments to the extent that actual and anticipated
operating results vary from those initially estimated at the time the valuation
allowance was established. The tax benefit associated with the intangible assets
is subject to statutory realization ratably over a fifteen-year period in total
if the Company achieves certain levels of taxable income.
 
NOTE 6.  SHARED SERVICES WITH HOUGHTON MIFFLIN
 
     The Company and Houghton Mifflin entered into an Administration and
Services Agreement ("Services Agreement"), which was effective upon completion
of the initial public offering described in Note 1 and under which Houghton
Mifflin provided directly some of the general services discussed in the
following paragraph that were previously provided to the Company. The term of
the Services Agreement extended through December 31, 1995. The fees charged for
general services under the Services Agreement, which are believed by the Company
to approximate amounts between unrelated parties, totaled $131,000 and $245,000
for 1995 and 1994, respectively.
 
     Prior to the completion of the initial public offering described in Note 1,
Houghton Mifflin provided various administrative services to the Company,
including, but not limited to, payroll, data processing, tax, legal, treasury,
human resources, employee benefits administration, financial and accounting,
executive services, and insurance administration. In addition, the Company's
employees participated in the various Houghton Mifflin benefit plans, and the
Company was charged for these benefits on the same basis as Houghton Mifflin
charged its other operating units. The following table lists the amounts charged
by Houghton Mifflin for the year ended December 31, 1993, along with offsetting
amounts recovered by the Company:
 
<TABLE>
<CAPTION>
                                                                   YEAR ENDED DECEMBER 31,
                                                                            1993
                                                                   -----------------------
                                                                      (IN THOUSANDS OF
                                                                          DOLLARS)
    <S>                                                            <C>
    Insurance and benefits.......................................          $   866
    General services.............................................              263
    Rent and occupancy costs.....................................              884
                                                                            ------
    Total charges................................................            2,013
    Less recovery for development work performed.................              (73)
                                                                            ------
    Net Charges..................................................          $ 1,940
                                                                            ======
</TABLE>
 
     The charges for rent and occupancy generally represent a pro-rata
pass-through of actual rent and related costs for the space occupied by the
Company. Following the initial public offering, these charges were covered by a
separate agreement. (See Note 7.)
 
NOTE 7.  OTHER TRANSACTIONS WITH HOUGHTON MIFFLIN
 
     The Company and Houghton Mifflin have various license agreements (the
"License Agreements") for the purpose of licensing certain database content from
published reference products of Houghton Mifflin's Trade and Reference Division
for use in certain of the Company's products. Included in the Company's cost of
revenues for the years ended December 31, 1995, 1994, and 1993, were royalties
to Houghton Mifflin for the licensing of this database content amounting to
 
                                      F-13
<PAGE>   48
 
                                INSO CORPORATION
 
           NOTES TO CONSOLIDATED FINANCIAL STATEMENTS -- (CONTINUED)
 
$700,000, $754,000, and $371,000, respectively. The terms of the License
Agreements are substantially the same as those in effect while the Company
operated as a division of Houghton Mifflin, except that the minimum royalty for
certain licenses of reference work content has been increased to 15% from 10%
only with respect to new OEM licenses entered into after January 1, 1994.
Effective December 31, 1994, the Company completed an agreement with Houghton
Mifflin whereby the rights of use and ownership of certain word lists were
transferred to the Company for $250,000, which was paid to Houghton Mifflin in
1995.
 
     During 1995, the book rights for the series of Information Please(R)
Almanacs were licensed back to Houghton Mifflin. (See Note 4.) In connection
with the book right licensing arrangement, the Company recognized approximately
$1,000,000 for the initial guaranteed royalty. As of December 31, 1995, $750,000
remained unpaid under the royalty arrangement and is included in accounts
receivable.
 
     Until May 1995, the Company's corporate offices occupied approximately
27,000 square feet in the Houghton Mifflin headquarters location in Boston,
Massachusetts. The Company and Houghton Mifflin entered into a Use and Occupancy
Agreement, which provided that the Company had the right to occupy that space
through December 31, 1995. That agreement was subject to termination by either
party with appropriate notice. On May 12, 1994, the Company notified Houghton
Mifflin that the Company was exercising its right to terminate the Use and
Occupancy Agreement effective May 12, 1995, in anticipation of the Company's
move to new office space in Boston. (See Note 11.) The Company's rent and
related costs under the agreement were consistent with past practice in that the
Company's costs were based upon a pro-rata share of the total Houghton Mifflin
headquarters space occupied and related services used by the Company. The
amounts incurred under this agreement for 1995 and 1994 totaled $219,000 and
$657,000, respectively.
 
     On April 1, 1994, Houghton Mifflin transferred to the Company's 87
employees, who had previously been in the employment of Houghton Mifflin, a
total of 17,400 shares of the Company's common stock. The transfer was accounted
for as a capital contribution equal to the value of common stock at the time of
transfer.
 
NOTE 8.  LINE OF CREDIT
 
     The Company has an unsecured line of credit for $1,000,000 available for
general use with no specific financial covenants. This line is supported by
commitment fees on the unused portion of the credit line. During 1995 and 1994,
the Company had no borrowings under this agreement.
 
NOTE 9.  STOCK PLANS
 
Stock Incentive Plan
 
     The Company has reserved 3,000,000 shares for issuance under the 1993 Stock
Incentive Plan ("1993 Plan"), which provides for the issuance of incentive stock
options, non-qualified stock options, unrestricted stock, restricted stock, and
performance share awards. Under the 1993 Plan, both incentive options and
non-qualified options may be granted to employees and consultants, and
non-qualified options may be granted to non-employee directors. The option
exercise price shall not be less than 100% of the fair market value of the
shares on date of grant in the case of incentive options and not less than 85%
of the fair market value of the shares on the date of grant in the case of
non-qualified options. The 1993 Plan also provides for the grant of performance
share awards to employees entitling the recipient to receive shares of common
stock based upon achievement of individual or Company performance goals. The
term of each option and the vesting periods for options and stock awards is
fixed by the Compensation Committee of the Company's Board of
 
                                      F-14
<PAGE>   49
 
                                INSO CORPORATION
 
           NOTES TO CONSOLIDATED FINANCIAL STATEMENTS -- (CONTINUED)
 
Directors. The term for incentive stock option grants may not exceed 10 years
from the date of grant. A summary of information regarding stock options is as
follows:
 
<TABLE>
<CAPTION>
                                                   AVAILABLE      OPTIONS         PRICE
                                                   FOR GRANT    OUTSTANDING     PER SHARE
                                                   ----------   -----------   -------------
    <S>                                            <C>          <C>           <C>
    1994
    Authorized...................................   1,000,000
    Granted......................................    (806,964)     806,964    $ 7.50-$13.18
    Exercised....................................                   (9,000)   $ 7.50
    Canceled.....................................       3,000       (3,000)   $ 7.50
    Restricted stock grant.......................     (47,036)
                                                                              -------------
                                                   ----------    ---------
    At December 31, 1994.........................     149,000      794,964    $ 7.50-$13.18
    1995
    Additional authorized........................   2,000,000
    Granted......................................  (1,494,250)   1,494,250    $16.75-$36.88
    Exercised....................................                  (77,000)   $ 7.50-$31.00
    Canceled.....................................      53,000      (53,000)   $ 7.50-$31.00
    Restricted stock grant.......................     (14,000)
                                                                              -------------
                                                   ----------    ---------
    At December 31, 1995.........................     693,750    2,159,214    $ 7.50-$36.88
                                                   ==========    =========    =============
</TABLE>
 
     The market value of the 14,000 and 47,036 of restricted shares awarded in
1995 and 1994 of $336,000 and $552,000, respectively has been recorded as
unearned compensation and is shown as a separate component of stockholders'
equity. Unearned compensation is being amortized to expense over the four- and
five-year vesting periods. Amortization totaled $173,000 and $46,000 at December
31, 1995 and 1994, respectively.
 
     At December 31, 1995, options to purchase 331,482 shares were exercisable.
 
Stock Purchase Plan
 
     Under the Company's 1993 Stock Purchase Plan, employees have the
opportunity to purchase the Company's common stock. The first offering under the
Stock Purchase Plan commenced on the effective date of the initial public
offering and concluded on June 30, 1994. Subsequent offerings begin on July 1
and January 1 of each year and conclude on December 31 and June 30,
respectively. The price at which the employee may purchase the common stock is
85% of the last reported sale price of the Company's common stock on the Nasdaq
National Market on the date the offering period commences or concludes,
whichever is lower. A total of 200,000 shares of common stock have been reserved
under this plan.
 
     Activity in the plan was as follows:
 
<TABLE>
<CAPTION>
                                                                   SHARES       PRICE
                                                                   -------   ------------
    <S>                                                            <C>       <C>
    1994
    Authorized...................................................  200,000
    Purchased during 1994........................................   12,386   $6.38
                                                                   -------
    Available for issuance at December 31, 1994..................  187,614
    1995
    Purchased during 1995........................................   26,492   $9.72-$14.51
                                                                   -------
    Available for issuance at December 31, 1995..................  161,122
                                                                   =======
</TABLE>
 
     In January 1996, for the six-month period ended December 31, 1995, 11,648
shares were issued at $25.50 per share.
 
                                      F-15
<PAGE>   50
 
                                INSO CORPORATION
 
           NOTES TO CONSOLIDATED FINANCIAL STATEMENTS -- (CONTINUED)
 
NOTE 10.  BENEFIT PLAN
 
     The Company has a 401(k) retirement savings plan ("401(k) Plan")
established in 1994 covering substantially all of the Company's domestic
employees. The Company has authorized 100,000 shares for issuance under the
Plan. Eligible employees are permitted to make pre-tax contributions, up to 15%
of their compensation subject to an annual limit, to seven funds, including
funds invested in the Company's common stock. Under the 401(k) Plan, the Company
may make contributions either in cash or common stock of the Company at the
discretion of the Company's Board of Directors. The contribution may match in
whole or in part the salary deferral contributions of the participants and/or
represent additional profit-sharing contributions tied to the Company's net
income performance. During 1995 and 1994, the Company's total contribution
amounted to approximately $197,000 and $180,000, respectively. The total 1994
Company contribution was matched in common stock of 10,336 shares during 1995.
 
NOTE 11.  LEASE COMMITMENTS
 
     The Company has various lease agreements for office space under operating
leases that expire in 2006. The Company's leases include certain renewal and
expansion options, escalation clauses for the Company's proportionate share of
increases in building maintenance costs, and periods of free rent. At December
31, 1995, future minimum lease commitments for noncancelable leases are as
follows:
 
<TABLE>
          <S>                                                           <C>
          1996........................................................  $  853,000
          1997........................................................   1,060,000
          1998........................................................   1,042,000
          1999........................................................   1,044,000
          2000........................................................   1,071,000
          Thereafter..................................................   5,938,000
</TABLE>
 
     Rent expense, including the amounts under the Use and Occupancy Agreement
with Houghton Mifflin, was approximately $836,000 in 1995. (See Notes 6 and 7.)
 
NOTE 12.  SUBSEQUENT EVENTS
 
     On January 9, 1996, the Company acquired all of the outstanding stock of
privately held ImageMark Software Labs, Inc. of Kansas City, Missouri, for
$5,500,000 in cash, which may be increased by $950,000 if certain 1996 revenue
levels are met or exceeded. ImageMark licenses graphical file format translation
technologies to original equipment manufacturers. The transaction will be
accounted for as a purchase. The Company also caused ImageMark to enter into
employment and noncompetition agreements with two key executives and made
aggregate payments of $1,000,000 under those agreements.
 
                                      F-16
<PAGE>   51
 
                                INSO CORPORATION
 
            PRO FORMA CONSOLIDATED FINANCIAL INFORMATION (UNAUDITED)
 
     The following unaudited pro forma consolidated statement of operations data
for the six months ended June 30, 1996 and the year ended December 31, 1995 give
pro forma effect to the Company's July 16, 1996 acquisition of EBT (including
payments by the Company for the EBT stock issuable upon exercise of outstanding
EBT stock options) as if such acquisition had occurred on January 1, 1996 and
1995, respectively, and the following unaudited pro forma consolidated balance
sheet data at June 30, 1996 gives pro forma effect to the EBT acquisition as if
it had occurred on June 30, 1996. The pro forma statement of operations data for
the six months ended June 30, 1996 and the year ended December 31, 1995 do not
reflect a charge of $34,300,000 for certain purchased in-process research and
development to be recorded by the Company in the third quarter of 1996. The
unaudited pro forma consolidated financial data are not necessarily indicative
of what the Company's financial condition or results of operations would have
been had the acquisition been consummated at the assumed dates.
 
<TABLE>
<CAPTION>
                                         SIX MONTHS ENDED JUNE 30, 1996                    YEAR ENDED DECEMBER 31, 1995
                                 ----------------------------------------------   -----------------------------------------------
                                                             PRO                                               PRO
                                                            FORMA                                             FORMA
                                    INSO         EBT       ADJUST-    PRO FORMA      INSO         EBT        ADJUST-    PRO FORMA
                                 HISTORICAL   HISTORICAL   MENTS(1)   COMBINED    HISTORICAL   HISTORICAL   MENTS(1)    COMBINED
                                 ----------   ----------   --------   ---------   ----------   ----------   ---------   ---------
                                                             (IN THOUSANDS, EXCEPT PER SHARE AMOUNTS)
<S>                              <C>          <C>          <C>        <C>         <C>          <C>          <C>         <C>
STATEMENT OF OPERATIONS DATA:
Net revenues...................   $ 27,605     $  7,488    $    --     $35,093     $ 43,387     $ 13,814     $    --     $57,201
Cost of revenues...............      3,845        1,604        336 (a)    5,785       5,792        2,603         672(a)    9,067
                                   -------      -------    -------     -------      -------      -------     -------     -------
Gross profit...................     23,760        5,884       (336 )    29,308       37,595       11,211        (672)     48,134
Operating Expenses:
  Sales and marketing..........      4,927        3,113        (25 )(b)    8,015      6,570        4,976         (50)(b)   11,496
  Product development..........      5,281        3,292        (25 )(b)    8,548      7,489        4,746         (50)(b)   12,185
  General and administrative...      3,951          911        (10 )(b)    4,852      6,458        1,426         (20)(b)    7,864
  Purchased in-process research
    and development............      4,400           --         --       4,400        5,500           --          --       5,500
                                   -------      -------    -------     -------      -------      -------     -------     -------
Total operating expenses.......     18,559        7,316        (60 )    25,815       26,017       11,148        (120)     37,045
Operating income (loss)........      5,201       (1,432)      (276 )     3,493       11,578           63        (552)     11,089
Net investment income
  (expense)....................      1,533          (54)                 1,479        1,468          (36)                  1,432
                                   -------      -------    -------     -------      -------      -------     -------     -------
Income (loss) before provision
  for income taxes.............      6,734       (1,486)      (276 )     4,972       13,046           27        (552)     12,521
Income tax expense (benefit)...      4,014         (338)                 3,676        7,052          (10)                  7,042
                                   -------      -------    -------     -------      -------      -------     -------     -------
Net income (loss)..............   $  2,720     $ (1,148)   $  (276 )   $ 1,296     $  5,994     $     37     $  (552)    $ 5,479
                                   -------      -------    -------     -------      -------      -------     -------     -------
Net income (loss) per share....   $   0.20     $  (0.08)   $ (0.02 )   $  0.09     $   0.49     $   0.00     $ (0.05)    $  0.45
Weighted average shares
  outstanding..................     13,690       13,690     13,690      13,690       12,228       12,228      12,228      12,228
</TABLE>
 
                                      F-17
<PAGE>   52
 
                                INSO CORPORATION
 
    PRO FORMA CONSOLIDATED FINANCIAL INFORMATION (UNAUDITED) -- (CONTINUED)
 
<TABLE>
<CAPTION>
                                                                                      JUNE 30, 1996
                                                              --------------------------------------------------------------
                                                                 INSO           EBT            PRO FORMA          PRO FORMA
                                                              HISTORICAL     HISTORICAL     ADJUSTMENTS(1)         COMBINED
                                                              ----------     ----------     ---------------       ----------
                                                                                      (IN THOUSANDS)
<S>                                                           <C>            <C>            <C>                   <C>
BALANCE SHEET DATA:
Current assets
  Cash, cash equivalents and marketable securities..........   $ 55,910        $  367          $ (38,408)(c)       $ 20,376
                                                                                                   2,507(d)
  Accounts receivable, net..................................     11,761         3,673                                15,434
  Other current assets......................................      1,132           291                                 1,423
  Refundable income taxes...................................                      336              3,325(e)           3,661
                                                                -------       -------            -------            -------
        Total current assets................................     68,803         4,667            (32,576)            40,894
Property and equipment, net.................................      3,250         2,286               (359)(f)          5,177
Royalty advances and other assets, net......................      2,304            98                                 2,402
Product development costs, net..............................      4,085           595              2,017(f)           6,697
Intangible assets, net......................................      9,484                                               9,484
Deferred income tax benefit, net............................      3,803           107                                 3,910
                                                                -------       -------            -------            -------
Total assets................................................   $ 91,729        $7,753          $ (30,918)          $ 68,564
                                                                =======       =======            =======            =======
Current liabilities
  Accounts payable and accrued liabilities..................   $  4,899        $3,018          $   2,746(g)        $ 10,663
  Dividend payable..........................................                                       1,898(h)           1,898
  Unearned revenue..........................................        449         1,858                                 2,307
  Royalties payable.........................................      1,748                                               1,748
  Due to Houghton Mifflin Company...........................        346                                                 346
  Current income taxes payable..............................      1,406                                               1,406
  Deferred income taxes.....................................      2,417           107             (1,685)(i)            839
  Subordinated notes payable and long-term debt.............                    1,726                                 1,726
                                                                -------       -------            -------            -------
        Total current liabilities...........................     11,265         6,709              2,959             20,933
Payable to stockholder......................................                                       1,467(j)           1,467
Redeemable preferred stock..................................                      286               (286)(k)              0
Total stockholders' equity..................................     80,464           758               (758)(k)         46,164
                                                                                                 (34,300)(l)
                                                                -------       -------            -------            -------
                                                                 80,464           758            (35,058)            46,164
                                                                -------       -------            -------            -------
Total liabilities and stockholders' equity..................   $ 91,729        $7,753          $ (30,918)          $ 68,564
                                                                =======       =======            =======            =======
</TABLE>
 
- ---------------
(1) A summary of the pro forma adjustments is set forth as follows:
     (a)  To record product development amortization expense using an
          amortization period of three years.
     (b) To adjust depreciation expense for the fair market value adjustment of
         the related assets.
     (c) To record operating cash paid for all outstanding Common and Preferred
         Stock, including the underlying common stock of the surviving EBT
         options.
     (d) To record cash received from the exercise of stock options.
     (e) To record income tax receivable resulting from tax benefits associated
         with the exercise of EBT stock options.
     (f)  To adjust assets acquired to estimated fair market value.
     (g) To record direct costs of the merger including legal and accounting
         services and appraisal fees and to record estimated costs to eliminate
         excess and duplicate activities relating to the merger.
     (h) To record dividend payable to the former stockholders of EBT.
     (i)  To record current deferred tax asset resulting from tax benefits to be
          derived from costs to eliminate excess and duplicate activities and
          the exercise of EBT stock options.
     (j)  To accrue additional merger consideration to be paid to the principal
          stockholder of EBT within 18 months of the closing date.
     (k) To eliminate EBT's redeemable preferred stock and stockholders' equity.
     (l)  To record the write-off of certain purchased technology under research
          and development.
 
                                      F-18
<PAGE>   53
                                                                              
================================================================================

NO PERSON HAS BEEN AUTHORIZED IN CONNECTION WITH THE OFFERING MADE HEREBY TO
GIVE ANY INFORMATION OR TO MAKE ANY REPRESENTATION NOT CONTAINED IN THIS
PROSPECTUS AND, IF GIVEN OR MADE, SUCH INFORMATION OR REPRESENTATION MUST NOT BE
RELIED UPON AS HAVING BEEN AUTHORIZED BY THE COMPANY OR ANY UNDERWRITER. THIS
PROSPECTUS DOES NOT CONSTITUTE AN OFFER TO SELL OR A SOLICITATION OF AN OFFER TO
BUY ANY OF THE SECURITIES OFFERED HEREBY TO ANY PERSON OR BY ANYONE IN ANY
JURISDICTION IN WHICH IT IS UNLAWFUL TO MAKE SUCH OFFER OR SOLICITATION. NEITHER
THE DELIVERY OF THIS PROSPECTUS NOR ANY SALE MADE HEREUNDER SHALL, UNDER ANY
CIRCUMSTANCES, CREATE ANY IMPLICATION THAT THE INFORMATION CONTAINED HEREIN IS
CORRECT AS OF ANY DATE SUBSEQUENT TO THE DATE HEREOF.
 
                               ------------------
 
                               TABLE OF CONTENTS
 
<TABLE>
<CAPTION>
                                        PAGE
                                        ----
<S>                                     <C>
Prospectus Summary....................    3
Risk Factors..........................    6
Use of Proceeds.......................    9
Price Range of Common Stock and
  Dividend Policy.....................   10
Capitalization........................   11
Selected Consolidated Financial
  Information.........................   12
Management's Discussion and Analysis
  of Financial Condition and Results
  of Operations.......................   14
Business..............................   20
Relationship with Houghton Mifflin....   27
Management............................   29
Underwriting..........................   32
Legal Matters.........................   33
Experts...............................   33
Available Information.................   34
Incorporation of Certain Documents by
  Reference...........................   34
Index to Consolidated Financial
  Statements..........................  F-1
</TABLE>
================================================================================
 
================================================================================

                                1,200,000 SHARES
                                  [INSO LOGO]
                                  COMMON STOCK
                             ----------------------
                                   PROSPECTUS
                             ----------------------
                               ALEX. BROWN & SONS
                                  INCORPORATED
                          ADAMS, HARKNESS & HILL, INC.
                             MONTGOMERY SECURITIES
                                          , 1996

================================================================================


© 2022 IncJournal is not affiliated with or endorsed by the U.S. Securities and Exchange Commission