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                                                                   EXHIBIT 10.22
                                                                                
                               IKOS SYSTEMS, INC.
                       1996 EMPLOYEE STOCK PURCHASE PLAN

              (AS AMENDED BY THE BOARD THROUGH NOVEMBER 12, 1997)


  1.  ESTABLISHMENT, PURPOSE AND TERM OF PLAN.
      --------------------------------------- 

      1.1  ESTABLISHMENT.  The IKOS Systems, Inc. 1996 Employee Stock Purchase
Plan (the "PLAN") is hereby established effective upon its approval by the
stockholders of the Company.

      1.2  PURPOSE.  The purpose of the Plan is to provide Eligible Employees of
the Participating Company Group with an opportunity to acquire a proprietary
interest in the Company through the purchase of Stock. The Company intends that
the Plan shall qualify as an "employee stock purchase plan" under Section 423 of
the Code (including any amendments or replacements of such section), and the
Plan shall be so construed.

      1.3  TERM OF PLAN.  The Plan shall continue in effect until the earlier of
its termination by the Board or the date on which all of the shares of Stock
available for issuance under the Plan have been issued.

  2.  DEFINITIONS AND CONSTRUCTION.
      ---------------------------- 

      2.1  DEFINITIONS.  Any term not expressly defined in the Plan but defined
for purposes of Section 423 of the Code shall have the same definition herein.
Whenever used herein, the following terms shall have their respective meanings
set forth below:

        (a)  "BOARD" means the Board of Directors of the Company. If one or more
Committees have been appointed by the Board to administer the Plan, "Board" also
means such Committee(s).

        (b)  "CODE" means the Internal Revenue Code of 1986, as amended, and any
applicable regulations promulgated thereunder.

        (c)  "COMMITTEE" means a committee of the Board duly appointed to
administer the Plan and having such powers as shall be specified by the Board.
Unless the powers of the Committee have been specifically limited, the Committee
shall have all of the powers of the Board granted herein, including, without
limitation, the power to amend or terminate the Plan at any time, subject to the
terms of the Plan and any applicable limitations imposed by law.

        (d)  "COMPANY" means IKOS Systems, Inc., a Delaware corporation, or any
successor corporation thereto.

        (e)  "COMPENSATION" means, with respect to an Offering Period under the
Plan, base salary, overtime, commissions and bonuses paid during such Offering
Period before deduction for any contributions to any plan maintained by a
Participating Company and described in Section 401(k) or Section 125 of the
Code. Compensation shall not include other incentive payments, long-term
disability, workers' compensation or any other payments not included in base
salary, overtime, commissions and bonuses.

        (f)  "ELIGIBLE EMPLOYEE" means an Employee who meets the requirements
set forth in Section 5 for eligibility to participate in the Plan.
<PAGE>
 
        (g)  "EMPLOYEE" means any person treated as an employee (including an
officer or a Director who is also treated as an employee) in the records of a
Participating Company and for purposes of Section 423 of the Code; provided,
however, that neither service as a Director nor payment of a director's fee
shall be sufficient to constitute employment for purposes of the Plan.

        (h)  "EXCHANGE ACT" means the Securities Exchange Act of 1934, as
amended.

        (i)  "FAIR MARKET VALUE" means, as of any date, if there is then a
public market for the Stock, the closing price of a share of Stock (or the mean
of the closing bid and asked prices of a share of Stock if the Stock is so
reported instead) as reported on the National Association of Securities Dealers
Automated Quotation ("NASDAQ") System, the NASDAQ National Market System or such
other national or regional securities exchange or market system constituting the
primary market for the Stock. If the relevant date does not fall on a day on
which the Stock is trading on NASDAQ, the NASDAQ National Market System or other
national or regional securities exchange or market system, the date on which the
Fair Market Value shall be established shall be the last day on which the Stock
was so traded prior to the relevant date, or such other appropriate day as shall
be determined by the Board, in its sole discretion. If there is then no public
market for the Stock, the Fair Market Value on any relevant date shall be as
determined by the Board without regard to any restriction other than a
restriction which, by its terms, will never lapse.

        (j)  "OFFERING" means an offering of Stock as provided in Section 6.

        (k)  "OFFERING DATE" means, for any Offering Period, the first day of
such Offering Period.

        (l)  "OFFERING PERIOD" means a period determined in accordance with
Section 6.1.

        (m)  "PARENT CORPORATION" means any present or future "parent
corporation" of the Company, as defined in Section 424(e) of the Code.

        (n)  "PARTICIPANT" means an Eligible Employee participating in the
Plan.

        (o)  "PARTICIPATING COMPANY" means the Company or any Parent Corporation
or Subsidiary Corporation designated by the Board for inclusion in the Plan. The
Board shall have the sole and absolute discretion to determine from time to time
which Parent Corporations or Subsidiary Corporations shall be Participating
Companies.

        (p)  "PARTICIPATING COMPANY GROUP" means, at any point in time, the
Company and all other corporations collectively which are then Participating
Companies.

        (q)  "PURCHASE DATE" means, for any Offering Period (or Purchase Period
if so determined by the Board in accordance with Section 6.2), the last day of
such period.

        (r)  "PURCHASE PERIOD" means any period determined in accordance with
Section 6.2.

        (s)  "PURCHASE PRICE" means the price at which a share of Stock may be
purchased pursuant to the Plan, as determined in accordance with Section 9.

        (t)  "PURCHASE RIGHT" means an option pursuant to the Plan to purchase
such shares of Stock as provided in Section 8 which may or may not be exercised
during an Offering Period. Such option arises from the right of a Participant to
withdraw such Participant's accumulated payroll deductions not previously
applied to the purchase of Stock under the Plan (if any) and terminate
participation in the Plan or any Offering therein at any time during an Offering
Period.
<PAGE>
 
        (u)  "STOCK" means the common stock of the Company, as adjusted from
time to time in accordance with Section 4.2.

        (v)  "SUBSIDIARY CORPORATION" means any present or future "subsidiary
corporation" of the Company, as defined in Section 424(f) of the Code.

      2.2  CONSTRUCTION.  Captions and titles contained herein are for
convenience only and shall not affect the meaning or interpretation of any
provision of the Plan. Except when otherwise indicated by the context, the
singular shall include the plural, the plural shall include the singular, and
use of the term "or" shall include the conjunctive as well as the disjunctive.

  3.  ADMINISTRATION.  The Plan shall be administered by the Board, including
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any duly appointed Committee of the Board.  All questions of interpretation of
the Plan or of any Purchase Right shall be determined by the Board and shall be
final and binding upon all persons having an interest in the Plan or such
Purchase Right.  Subject to the provisions of the Plan, the Board shall
determine all of the relevant terms and conditions of Purchase Rights granted
pursuant to the Plan; provided, however, that all Participants granted Purchase
Rights pursuant to the Plan shall have the same rights and privileges within the
meaning of Section 423(b)(5) of the Code.  All expenses incurred in connection
with the administration of the Plan shall be paid by the Company.

  4.  SHARES SUBJECT TO PLAN.
      ---------------------- 

      4.1  MAXIMUM NUMBER OF SHARES ISSUABLE.  Subject to adjustment as provided
in Section 4.2, the maximum aggregate number of shares of Stock that may be
issued under the Plan shall be two hundred fifty thousand (250,000) and shall
consist of authorized but unissued or reacquired shares of the Stock, or any
combination thereof. If an outstanding Purchase Right for any reason expires or
is terminated or canceled, the shares of Stock allocable to the unexercised
portion of such Purchase Right shall again be available for issuance under the
Plan.

      4.2  ADJUSTMENTS FOR CHANGES IN CAPITAL STRUCTURE.  In the event of any
stock dividend, stock split, reverse stock split, recapitalization, combination,
reclassification or similar change in the capital structure of the Company, or
in the event of any merger (including a merger effected for the purpose of
changing the Company's domicile), sale of assets or other reorganization in
which the Company is a party, appropriate adjustments shall be made in the
number and class of shares subject to the Plan, to the Per Offering Share Limit
set forth in Section 8.1 and to each Purchase Right and in the Purchase Price.

  5.  ELIGIBILITY.
      ----------- 

      5.1  EMPLOYEES ELIGIBLE TO PARTICIPATE.  Any Employee of a Participating
Company shall be eligible to participate in the Plan except the following:

        (a)  Employees who have not completed at least six (6) months of
continuous employment with the Participating Company Group as of the
commencement of an Offering Period; provided, however, that this subsection (a)
shall not apply to Offering Periods commencing on and after August 1, 1996,
except with respect to those employees whose transactions in Stock are subject
to Section 16 of the Exchange Act ("INSIDERS");

        (b)  Employees who are customarily employed by the Participating Company
Group for twenty (20) hours or less per week; and

        (c)  Employees who own or hold options to purchase or who, as a result
of participation in the Plan, would own or hold options to purchase, stock of
the Company or of any Parent Corporation or Subsidiary Corporation possessing
five percent (5%) or more of the total combined voting power or value of all
classes of stock of such corporation within the meaning of Section 423(b)(3) of
the Code.
<PAGE>
 
      5.2  LEASED EMPLOYEES EXCLUDED.  Notwithstanding anything herein to the
contrary, any individual performing services for a Participating Company solely
through a leasing agency or employment agency shall not be deemed an "Employee"
of such Participating Company.

  6.  OFFERINGS.
      --------- 

      6.1  OFFERING PERIODS.  Except as otherwise set forth below, the Plan
shall be implemented by sequential Offerings of approximately six (6) months
duration (an "OFFERING PERIOD"). The first Offering Period shall commence on
February 8, 1996 and end on July 31, 1996. Subsequent Offerings shall commence
on the first days of February and August of each year and end on the last days
of the next July and January, respectively, occurring thereafter.
Notwithstanding the foregoing, the Board may establish a different term for one
or more Offerings or different commencing or ending dates for such Offerings;
provided, however, that no Offering may exceed a term of twenty-seven (27)
months. An Employee who becomes an Eligible Employee after an Offering Period
has commenced shall not be eligible to participate in such Offering but may
participate in any subsequent Offering provided such Employee is still an
Eligible Employee as of the commencement of any such subsequent Offering.
Eligible Employees may not participate in more than one Offering at a time. In
the event the first or last day of an Offering Period is not a business day, the
Company shall specify the business day that will be deemed the first or last
day, as the case may be, of the Offering Period.

      6.2  PURCHASE PERIODS.  If the Board shall so determine, in its
discretion, each Offering Period may consist of two (2) or more consecutive
purchase periods having such duration as the Board shall specify (individually,
a "PURCHASE PERIOD"), and the last day of each such Purchase Period shall be a
Purchase Date. In the event the first or last day of a Purchase Period is not a
business day, the Company shall specify the business day that will be deemed the
first or last day, as the case may be, of the Purchase Period.

      6.3  GOVERNMENTAL APPROVAL; STOCKHOLDER APPROVAL.  Notwithstanding any
other provision of the Plan to the contrary, any Purchase Right granted pursuant
to the Plan shall be subject to (a) obtaining all necessary governmental
approvals or qualifications of the sale or issuance of the Purchase Rights or
the shares of Stock and (b) obtaining stockholder approval of the Plan.

  7.  PARTICIPATION IN THE PLAN.
      ------------------------- 

      7.1  INITIAL PARTICIPATION.  An Eligible Employee shall become a
Participant on the first Offering Date after satisfying the eligibility
requirements of Section 5 and delivering to the Company's payroll office or
other office designated by the Company not later than the close of business for
such office on the last business day before such Offering Date (the
"SUBSCRIPTION DATE") a subscription agreement indicating the Employee's election
to participate in the Plan and authorizing payroll deductions. An Eligible
Employee who does not deliver a subscription agreement to the Company's payroll
or other designated office on or before the Subscription Date shall not
participate in the Plan for that Offering Period or for any subsequent Offering
Period unless such Employee subsequently enrolls in the Plan by filing a
subscription agreement with the Company by the Subscription Date for such
subsequent Offering Period. The Company may, from time to time, change the
Subscription Date as deemed advisable by the Company in its sole discretion for
proper administration of the Plan.

      7.2  CONTINUED PARTICIPATION.  A Participant shall automatically
participate in the Offering Period commencing immediately after the final
Purchase Date of each Offering Period in which the Participant participates
until such time as such Participant (a) ceases to be an Eligible Employee, (b)
withdraws from the Plan pursuant to Section 13.2 or (c) terminates employment as
provided in Section 14. If a Participant automatically may participate in a
subsequent Offering Period pursuant to this Section 7.2, then the Participant is
not required to file any additional subscription agreement for such subsequent
Offering Period in order to continue participation in the Plan. However, a
Participant may file a subscription agreement with respect to a subsequent
Offering Period if the Participant desires to change any of the Participant's
elections contained in the Participant's then effective subscription agreement.
<PAGE>
 
  8.  RIGHT TO PURCHASE SHARES.
      ------------------------ 

      8.1  PURCHASE RIGHT.  Except as set forth below, during an Offering Period
each Participant in such Offering Period shall have a Purchase Right consisting
of the right to purchase that number of whole shares of Stock arrived at by
dividing Twelve Thousand Five Hundred Dollars ($12,500) by the Fair Market Value
of a share of Stock on the Offering Date of such Offering Period; provided,
however, that such number shall not exceed five hundred (500) shares (the "PER
OFFERING SHARE LIMIT").  Shares of Stock may only be purchased through a
Participant's payroll deductions pursuant to Section 10.

      8.2  PRO RATA ADJUSTMENT OF PURCHASE RIGHT.  Notwithstanding the
foregoing, if the Board shall establish an Offering Period of less than five and
one-half (52) months or more than six and one-half (62) months in duration, (a)
the dollar amount in Section 8.1 shall be determined by multiplying $2,083.33 by
the number of months in the Offering Period and rounding to the nearest whole
dollar, and (b) the Per Offering Share Limit shall be determined by multiplying
83.33 shares by the number of months in the Offering Period and rounding to the
nearest whole share. For purposes of the preceding sentence, fractional months
shall be rounded to the nearest whole month.

  9.  PURCHASE PRICE.  The Purchase Price at which each share of Stock may be
      --------------                                                         
acquired in a given Offering Period pursuant to the exercise of all or any
portion of a Purchase Right granted under the Plan shall be set by the Board;
provided, however, that the Purchase Price shall not be less than eighty-five
percent (85%) of the lesser of (a) the Fair Market Value of a share of Stock on
the Offering Date of such Offering Period, or (b) the Fair Market Value of a
share of Stock on the Purchase Date of such Offering Period.  Unless otherwise
provided by the Board prior to the commencement of an Offering Period, the
Purchase Price for that Offering Period shall be eighty-five percent (85%) of
the lesser of (a) the Fair Market Value of a share of Stock on the Offering
Date, or (b) the Fair Market Value of a share of Stock on the Purchase Date.

  10.  ACCUMULATION OF PURCHASE PRICE THROUGH PAYROLL DEDUCTION.  Shares of
       --------------------------------------------------------            
Stock which are acquired pursuant to the exercise of all or any portion of a
Purchase Right for an Offering Period may be paid for only by means of payroll
deductions from the Participant's Compensation accumulated during the Offering
Period.  Except as set forth below, the amount of Compensation to be deducted
from a Participant's Compensation on each payday during an Offering Period shall
be determined by the Participant's subscription agreement.

      10.1  COMMENCEMENT OF PAYROLL DEDUCTIONS.  Payroll deductions shall
commence on the first payday following the Offering Date and shall continue to
the end of the Offering Period unless sooner altered or terminated as provided
in the Plan.

      10.2  LIMITATIONS ON PAYROLL DEDUCTIONS.  The amount of payroll deductions
with respect to the Plan for any Participant on any payday shall be in one
percent (1%) increments not to exceed ten percent (10%) of the Participant's
Compensation on such payday.  Notwithstanding the foregoing, the Board may
change the limits on payroll deductions effective as of a future Offering Date,
as determined by the Board.  Amounts deducted from Compensation shall be reduced
by any amounts contributed by the Participant and applied to the purchase of
Company stock pursuant to any other employee stock purchase plan qualifying
under Section 423 of the Code.

      10.3  ELECTION TO DECREASE OR STOP PAYROLL DEDUCTIONS.  During an Offering
Period, a Participant may elect to decrease the amount deducted or stop
deductions from his or her Compensation by filing an amended subscription
agreement with the Company on or before the "Change Notice Date."  The "CHANGE
NOTICE DATE" shall initially be the seventh (7th) day prior to the end of the
first pay period for which such election is to be effective; however, the
Company may change such Change Notice Date from time to time

      10.4  PARTICIPANT ACCOUNTS.  Individual Plan accounts shall be maintained
for each Participant. All payroll deductions from a Participant's Compensation
shall be credited to such account 
<PAGE>
 
and shall be deposited with the general funds of the Company. All payroll
deductions received or held by the Company may be used by the Company for any
corporate purpose.

      10.5  NO INTEREST PAID.  Interest shall not be paid on sums deducted from
a Participant's Compensation pursuant to the Plan.

      10.6  COMPANY ESTABLISHED PROCEDURES.  The Company may, from time to time,
establish or change (a) a minimum required payroll deduction amount for
participation in an Offering, (a) limitations on the frequency or number of
changes in the rate of payroll deduction during an Offering, (c) an exchange
ratio applicable to amounts withheld in a currency other than U.S. dollars, (d)
payroll deduction in excess of or less than the amount designated by a
Participant in order to adjust for delays or mistakes in the Company's
processing of subscription agreements, (e) the date(s) and manner by which the
Fair Market Value of a share of Stock is determined for purposes of
administration of the Plan, or (vi) such other limitations or procedures as
deemed advisable by the Company in the Company's sole discretion which are
consistent with the Plan and in accordance with the requirements of Section 423
of the Code.

  11.  PURCHASE OF SHARES.
       ------------------ 

      11.1  EXERCISE OF PURCHASE RIGHT.  On each Purchase Date of an Offering
Period, each Participant who has not withdrawn from the Offering or whose
participation in the Offering has not terminated on or before such Purchase Date
shall automatically acquire pursuant to the exercise of the Participant's
Purchase Right the number of whole shares of Stock arrived at by dividing the
total amount of the Participant's accumulated payroll deductions for the
Offering Period not previously applied toward the purchase of Stock by the
Purchase Price; provided, however, in no event shall the number of shares
purchased by the Participant during an Offering Period exceed the number of
shares subject to the Participant's Purchase Right.  No shares of Stock shall be
purchased on a Purchase Date on behalf of a Participant whose participation in
the Offering or the Plan has terminated on or before such Purchase Date.

      11.2  RETURN OF CASH BALANCE.  Any cash balance remaining in the
Participant's Plan account shall be refunded to the Participant as soon as
practicable after the Purchase Date. However, in the event the cash to be
returned to a Participant pursuant to the preceding sentence is an amount less
than the amount necessary to purchase a whole share of Stock, the Company may
establish procedures whereby such cash is maintained in the Participant's Plan
account and applied toward the purchase of shares of Stock in the subsequent
Offering Period (or Purchase Period, as the case may be).

      11.3  TAX WITHHOLDING.  At the time a Participant's Purchase Right is
exercised, in whole or in part, or at the time a Participant disposes of some or
all of the shares of Stock he or she acquires under the Plan, the Participant
shall make adequate provision for the foreign, federal, state and local tax
withholding obligations of the Participating Company Group, if any, which arise
upon exercise of the Purchase Right or upon such disposition of shares,
respectively.  The Participating Company Group may, but shall not be obligated
to, withhold from the Participant's compensation the amount necessary to meet
such withholding obligations.

      11.4  EXPIRATION OF PURCHASE RIGHT.  Any portion of a Participant's
Purchase Right remaining unexercised after the end of the Offering Period to
which such Purchase Right relates shall expire immediately upon the end of such
Offering Period.

  12. LIMITATIONS ON PURCHASE OF SHARES; RIGHTS AS A STOCKHOLDER.
      ---------------------------------------------------------- 

      12.1  FAIR MARKET VALUE LIMITATION.  Notwithstanding any other provision
of the Plan, no Participant shall be entitled to purchase shares of Stock under
the Plan (or any other employee stock purchase plan which is intended to meet
the requirements of Section 423 of the Code sponsored by the Company or a Parent
Corporation or Subsidiary Corporation) at a rate which exceeds $25,000 in Fair
Market Value, which Fair Market Value is determined for shares purchased during
a given Offering Period as of the Offering Date for such Offering Period (or
such other limit as may be imposed by the Code), for 
<PAGE>
 
each calendar year in which the Participant participates in the Plan (or any
other employee stock purchase plan described in this sentence).

      12.2  PRO RATA ALLOCATION.  In the event the number of shares of Stock
which might be purchased by all Participants in the Plan exceeds the number of
shares of Stock available in the Plan, the Company shall make a pro rata
allocation of the remaining shares in as uniform a manner as shall be
practicable and as the Company shall determine to be equitable.

      12.3  RIGHTS AS A STOCKHOLDER AND EMPLOYEE.  A Participant shall have no
rights as a stockholder by virtue of the Participant's participation in the Plan
until the date of the issuance of a stock certificate for the shares of Stock
being purchased pursuant to the exercise of the Participant's Purchase Right.
No adjustment shall be made for cash dividends or distributions or other rights
for which the record date is prior to the date such stock certificate is issued.
Nothing herein shall confer upon a Participant any right to continue in the
employ of the Participating Company Group or interfere in any way with any right
of the Participating Company Group to terminate the Participant's employment at
any time.

 13.  WITHDRAWAL.
      ---------- 

      13.1  WITHDRAWAL FROM AN OFFERING.  A Participant may withdraw from an
Offering by signing and delivering to the Company's payroll or other designated
office a written notice of withdrawal on a form provided by the Company for such
purpose.  Such withdrawal may be elected at any time prior to the end of an
Offering Period; provided, however, if a Participant withdraws after a Purchase
Date, the withdrawal shall not affect shares of Stock acquired by the
Participant on such Purchase Date.  Unless otherwise indicated, withdrawal from
an Offering shall not result in a withdrawal from the Plan or any succeeding
Offering therein.  A Participant is prohibited from again participating in an
Offering at any time following withdrawal from such Offering.  The Company may
impose, from time to time, a requirement that the notice of withdrawal be on
file with the Company's payroll office or other designated office for a
reasonable period prior to the effectiveness of the Participant's withdrawal
from an Offering.

      13.2  WITHDRAWAL FROM THE PLAN.  A Participant may withdraw from the Plan
by signing and delivering to the Company's payroll office or other designated
office a written notice of withdrawal on a form provided by the Company for such
purpose. Withdrawals made after a Purchase Date shall not affect shares of Stock
acquired by the Participant on such Purchase Date. In the event a Participant
voluntarily elects to withdraw from the Plan, the Participant may not resume
participation in the Plan during the same Offering Period, but may participate
in any subsequent Offering under the Plan by again satisfying the requirements
of Sections 5 and 7.1. The Company may impose, from time to time, a requirement
that the notice of withdrawal be on file with the Company's payroll office or
other designated office for a reasonable period prior to the effectiveness of
the Participant's withdrawal from the Plan.

      13.3  RETURN OF PAYROLL DEDUCTIONS.  Upon a Participant's withdrawal from
an Offering or the Plan pursuant to Sections 13.1 or 13.2, respectively, the
Participant's accumulated payroll deductions which have not been applied toward
the purchase of shares of Stock shall be returned as soon as practicable after
the withdrawal, without the payment of any interest, to the Participant, and the
Participant's interest in the Offering or the Plan, as applicable, shall
terminate. Such accumulated payroll deductions may not be applied to any other
Offering under the Plan.

  14. TERMINATION OF EMPLOYMENT OR ELIGIBILITY.  Termination of a Participant's
      ----------------------------------------                                 
employment with the Company for any reason, including retirement, disability or
death or the failure of a Participant to remain an Eligible Employee, shall
terminate the Participant's participation in the Plan immediately.  In such
event, the payroll deductions credited to the Participant's Plan account since
the last Purchase Date shall, as soon as practicable, be returned to the
Participant or, in the case of the Participant's death, to the Participant's
legal representative, and all of the Participant's rights under the Plan shall
terminate.  Interest shall not be paid on sums returned to a Participant
pursuant to this Section 14.  A Participant whose participation has been so
terminated may again become eligible to participate in the Plan by again
satisfying the requirements of Sections 5 and 7.1.
<PAGE>
 
  15. TRANSFER OF CONTROL.
      ------------------- 

      15.1  DEFINITIONS.

        (a)  An "OWNERSHIP CHANGE EVENT" shall be deemed to have occurred if any
of the following occurs with respect to the Company: (i) the direct or indirect
sale or exchange in a single or series of related transactions by the
stockholders of the Company of more than fifty percent (50%) of the voting stock
of the Company; (ii) a merger or consolidation in which the Company a party;
(iii) the sale, exchange, or transfer of all or substantially all of the assets
of the Company; or (iv) a liquidation or dissolution of the Company.

        (b)  A "TRANSFER OF CONTROL" shall mean an Ownership Change Event or a
series of related Ownership Change Events (collectively, the "TRANSACTION")
wherein the stockholders of the Company immediately before the Transaction do
not retain immediately after the Transaction, in substantially the same
proportions as their ownership of shares of the Company's voting stock
immediately before the Transaction, direct or indirect beneficial ownership of
more than fifty percent (50%) of the total combined voting power of the
outstanding voting stock of the Company or the corporation or corporations to
which the assets of the Company were transferred (the "TRANSFEREE
CORPORATION(S)"), as the case may be. For purposes of the preceding sentence,
indirect beneficial ownership shall include, without limitation, an interest
resulting from ownership of the voting stock of one or more corporations which,
as a result of the Transaction, own the Company or the Transferee
Corporation(s), as the case may be, either directly or through one or more
subsidiary corporations. The Board shall have the right to determine whether
multiple sales or exchanges of the voting stock of the Company or multiple
Ownership Change Events are related, and its determination shall be final,
binding and conclusive.

      15.2  EFFECT OF TRANSFER OF CONTROL ON PURCHASE RIGHTS.  In the event of a
Transfer of Control, the surviving, continuing, successor, or purchasing
corporation or parent corporation thereof, as the case may be (the "ACQUIRING
CORPORATION"), may assume the Company's rights and obligations under the Plan or
substitute substantially equivalent Purchase Rights for stock of the Acquiring
Corporation.  If the Acquiring Corporation elects not to assume or substitute
for the outstanding Purchase Rights, the Board may, in its sole discretion and
notwithstanding any other provision herein to the contrary, adjust the Purchase
Date of the then current Purchase Period to a date on or before the date of the
Transfer of Control, but shall not adjust the number of shares of Stock subject
to any Purchase Right.  All Purchase Rights which are neither assumed or
substituted for by the Acquiring Corporation in connection with the Transfer of
Control nor exercised as of the date of the Transfer of Control shall terminate
and cease to be outstanding effective as of the date of the Transfer of Control.
Notwithstanding the foregoing, if the corporation the stock of which is subject
to the outstanding Purchase Rights immediately prior to an Ownership Change
Event described in Section 15.1(a)(i) constituting a Transfer of Control is the
surviving or continuing corporation and immediately after such Ownership Change
Event less than fifty percent (50%) of the total combined voting power of its
voting stock is held by another corporation or by other corporations that are
members of an affiliated group within the meaning of section 1504(a) of the Code
without regard to the provisions of section 1504(b) of the Code, the outstanding
Purchase Rights shall not terminate unless the Board otherwise provides in its
sole discretion.

  16. NONTRANSFERABILITY OF PURCHASE RIGHTS.  A Purchase Right may not be
      -------------------------------------                              
transferred in any manner otherwise than by will or the laws of descent and
distribution and shall be exercisable during the lifetime of the Participant
only by the Participant.  The Company, in its absolute discretion, may impose
such restrictions on the transferability of the shares purchasable upon the
exercise of a Purchase Right as it deems appropriate and any such restriction
shall be set forth in the respective subscription agreement and may be referred
to on the certificates evidencing such shares.

  17. REPORTS.  Each Participant who has exercised all or part of his or her
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Purchase Right shall receive, as soon as practicable after the Purchase Date, a
report of such Participant's Plan account setting forth the total payroll
deductions accumulated, the number of shares of Stock purchased, the Purchase
Price for such shares, the date of purchase and the remaining cash balance to be
refunded or retained in the Participant's Plan account pursuant to Section 11.2,
if any.  Each Participant shall be provided information concerning the Company
equivalent to that information generally made available to the Company's common
stockholders.
<PAGE>
 
  18. RESTRICTION ON ISSUANCE OF SHARES.  The issuance of shares under the Plan
      ---------------------------------                                        
shall be subject to compliance with all applicable requirements of foreign,
federal or state law with respect to such securities.  A Purchase Right may not
be exercised if the issuance of shares upon such exercise would constitute a
violation of any applicable foreign, federal or state securities laws or other
law or regulations.  In addition, no Purchase Right may be exercised unless (a)
a registration statement under the Securities Act of 1933, as amended, shall at
the time of exercise of the Purchase Right be in effect with respect to the
shares issuable upon exercise of the Purchase Right, or (b) in the opinion of
legal counsel to the Company, the shares issuable upon exercise of the Purchase
Right may be issued in accordance with the terms of an applicable exemption from
the registration requirements of said Act.  The inability of the Company to
obtain from any regulatory body having jurisdiction the authority, if any,
deemed by the Company's legal counsel to be necessary to the lawful issuance and
sale of any shares under the Plan shall relieve the Company of any liability in
respect of the failure to issue or sell such shares as to which such requisite
authority shall not have been obtained.  As a condition to the exercise of a
Purchase Right, the Company may require the Participant to satisfy any
qualifications that may be necessary or appropriate, to evidence compliance with
any applicable law or regulation, and to make any representation or warranty
with respect thereto as may be requested by the Company.

  19. LEGENDS.  The Company may at any time place legends or other identifying
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symbols referencing any applicable foreign, federal or state securities law
restrictions or any provision convenient in the administration of the Plan on
some or all of the certificates representing shares of Stock issued under the
Plan.  The Participant shall, at the request of the Company, promptly present to
the Company any and all certificates representing shares acquired pursuant to a
Purchase Right in the possession of the Participant in order to carry out the
provisions of this Section.  Unless otherwise specified by the Company, legends
placed on such certificates may include but shall not be limited to the
following:

      "THE SHARES EVIDENCED BY THIS CERTIFICATE WERE ISSUED BY THE CORPORATION
TO THE REGISTERED HOLDER UPON THE PURCHASE OF SHARES UNDER AN EMPLOYEE STOCK
PURCHASE PLAN AS DEFINED IN SECTION 423 OF THE INTERNAL REVENUE CODE OF 1986, AS
AMENDED. THE TRANSFER AGENT FOR THE SHARES EVIDENCED HEREBY SHALL NOTIFY THE
CORPORATION IMMEDIATELY OF ANY TRANSFER OF THE SHARES BY THE REGISTERED HOLDER
HEREOF MADE ON OR BEFORE ______________, 19__. THE REGISTERED HOLDER SHALL HOLD
ALL SHARES PURCHASED UNDER THE PLAN IN THE REGISTERED HOLDER'S NAME (AND NOT IN
THE NAME OF ANY NOMINEE) PRIOR TO THIS DATE."

  20. NOTIFICATION OF SALE OF SHARES.  The Company may require the Participant
      ------------------------------                                          
to give the Company prompt notice of any disposition of shares acquired by
exercise of a Purchase Right within two years from the date of granting such
Purchase Right or one year from the date of exercise of such Purchase Right.
The Company may require that until such time as a Participant disposes of shares
acquired upon exercise of a Purchase Right, the Participant shall hold all such
shares in the Participant's name (and not in the name of any nominee) until the
lapse of the time periods with respect to such Purchase Right referred to in the
preceding sentence.  The Company may direct that the certificates evidencing
shares acquired by exercise of a Purchase Right refer to such requirement to
give prompt notice of disposition.

  21. AMENDMENT OR TERMINATION OF THE PLAN.  The Board may at any time amend or
      ------------------------------------                                     
terminate the Plan, except that (a) such termination shall not affect Purchase
Rights previously granted under the Plan, except as permitted under the Plan,
and (b) no amendment may adversely affect a Purchase Right previously granted
under the Plan (except to the extent permitted by the Plan or as may be
necessary to qualify the Plan as an employee stock purchase plan pursuant to
Section 423 of the Code or to obtain qualification or registration of the shares
of Stock under applicable foreign, federal or state securities laws).  In
addition, an amendment to the Plan must be approved by the stockholders of the
Company within twelve (12) months of the adoption of such amendment if such
amendment would authorize the sale of more 
<PAGE>
 
shares than are authorized for issuance under the Plan or would change the
definition of the corporations that may be designated by the Board as
Participating Companies.

  IN WITNESS WHEREOF, the undersigned Secretary of the Company certifies that
the foregoing is the IKOS Systems, Inc. 1996 Employee Stock Purchase Plan as
duly adopted by the Board on October 26, 1995 and amended by the Board through
November 12, 1997.


                                    /s/ Joseph W. Rockom
                                    -------------------------             
                                    Secretary