QUICKTURN DESIGN SYSTEMS, INC.

                       1996 SUPPLEMENTAL STOCK PLAN, AS AMENDED

     1.   PURPOSES OF THE PLAN.  The purposes of this Plan are:

            -       to attract and retain the best available personnel for
                    positions of substantial responsibility, 

            -       to provide additional incentive to key Employees, Directors
                    and Consultants, and 

            -       to promote the success of the Company's business.  

     Options granted under the Plan will be Nonstatutory Stock Options.  

     2.   DEFINITIONS.  As used herein, the following definitions shall apply:

          (a)  "ADMINISTRATOR" means the Board or any of its Committees as 
shall be administering the Plan, in accordance with Section 4 of the Plan.

          (b)  "APPLICABLE LAWS" means the requirements relating to the 
administration of stock option plans under U. S. state corporate laws, U.S. 
federal and state securities laws, the Code, any stock exchange or quotation 
system on which the Common Stock is listed or quoted and the applicable laws 
of any foreign country or jurisdiction where Options are granted under the 
Plan.

          (c)  "BOARD" means the Board of Directors of the Company.

          (d)  "CODE" means the Internal Revenue Code of 1986, as amended.

          (e)  "COMMITTEE"  means a committee of Directors appointed by the 
Board in accordance with Section 4 of the Plan.

          (f)  "COMMON STOCK" means the Common Stock of the Company.

          (g)  "COMPANY" means Quickturn Design Systems, Inc., a Delaware 
corporation.

          (h)  "CONSULTANT" means any person, including an advisor, engaged 
by the Company or a Parent or Subsidiary to render services to such entity.

          (i)  "DIRECTOR" means a member of the Board.

          (j)  "DISABILITY" means total and permanent disability as defined 
in Section 22(e)(3) of the Code.



          (k)  "EMPLOYEE" means any person, including Officers, employed by 
the Company or any Parent or Subsidiary of the Company.  A Service Provider 
shall not cease to be an Employee in the case of (i) any leave of absence 
approved by the Company or (ii) transfers between locations of the Company or 
between the Company, its Parent, any Subsidiary, or any successor.  Neither 
service as a Director nor payment of a director's fee by the Company shall be 
sufficient to constitute "employment" by the Company.

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

          (m)  "FAIR MARKET VALUE" means, as of any date, the value of Common 
Stock determined as follows:

               (i)    If the Common Stock is listed on any established stock 
exchange or a national market system, including without limitation the Nasdaq 
National Market or The Nasdaq SmallCap Market of The Nasdaq Stock Market, its 
Fair Market Value shall be the closing sales price for such stock (or the 
closing bid, if no sales were reported) as quoted on such exchange or system 
for the last market trading day prior to the time of determination, as 
reported in THE WALL STREET JOURNAL or such other source as the Administrator 
deems reliable;

               (ii)   If the Common Stock is regularly quoted by a recognized 
securities dealer but selling prices are not reported, the Fair Market Value 
of a Share of Common Stock shall be the mean between the high bid and low 
asked prices for the Common Stock on the last market trading day prior to the 
day of determination, as reported in THE WALL STREET JOURNAL or such other 
source as the Administrator deems reliable;

               (iii)  In the absence of an established market for the Common 
Stock, the Fair Market Value shall be determined in good faith by the 
Administrator.

          (n)  "NONSTATUTORY STOCK OPTION" means an Option not intended to 
qualify as an incentive stock option within the meaning of Section 422 of the 
Code and the regulations promulgated thereunder.

          (o)  "NOTICE OF GRANT" means a written or electronic notice 
evidencing certain terms and conditions of an individual Option grant.  The 
Notice of Grant is part of the Option Agreement.

          (p)  "OFFICER" means a person who is an officer of the Company 
within the meaning of Section 16 of the Exchange Act and the rules and 
regulations promulgated thereunder.

          (q)  "OPTION" means a stock option granted pursuant to the Plan.

          (r)  "OPTION AGREEMENT" means an agreement between the Company and 
an Optionee evidencing the terms and conditions of an individual Option 
grant.  The Option Agreement is subject to the terms and conditions of the 
Plan.

                                       -2-



          (s)  "OPTION EXCHANGE PROGRAM" means a program whereby 
outstanding options are surrendered in exchange for options with a lower 
exercise price.

          (t)  "OPTIONED STOCK" means the Common Stock subject to an Option.

          (u)  "OPTIONEE" means the holder of an outstanding Option granted 
under the Plan.

          (v)  "PARENT" means a "parent corporation," whether now or 
hereafter existing, as defined in Section 424(e) of the Code.

          (w)  "PLAN" means this 1996 Supplemental Stock Plan, as amended.

          (x)  "SERVICE PROVIDER" means an Employee, Director or Consultant. 

          (y)  "SHARE" means a share of the Common Stock, as adjusted in 
accordance with Section 13 of the Plan.

          (z)  "SUBSIDIARY" means a "subsidiary corporation", whether now or 
hereafter existing, as defined in Section 424(f) of the Code.

     3.   STOCK SUBJECT TO THE PLAN.  Subject to the provisions of Section 13 
of the Plan, the maximum aggregate number of Shares which may be optioned and 
sold under the Plan is 1,000,000 Shares.  The Shares may be authorized, but 
unissued, or reacquired Common Stock.  

          If an Option expires or becomes unexercisable without having been 
exercised in full, or is surrendered pursuant to an Option Exchange Program, 
the unpurchased Shares which were subject thereto shall become available for 
future grant or sale under the Plan (unless the Plan has terminated).  Shares 
that have actually been issued under the Plan shall not be returned to the 
Plan and shall not become available for future distribution under the Plan, 
except that if unvested Shares are repurchased by the Company at their 
original purchase price, such Shares shall become available for future grant 
under the Plan. 

     4.   ADMINISTRATION OF THE PLAN.

          (a)  PROCEDURE.  The Plan shall be administered by (A) the Board or 
(B) a Committee, which committee shall be constituted to satisfy Applicable 
Laws. 

          (b)  RULE 16b-3.  To the extent desirable to qualify transactions 
hereunder as exempt under Rule 16b-3, the transactions contemplated hereunder 
shall be structured to satisfy the requirements for exemption under Rule 
16b-3. 

                                       -3-



          (c)  POWERS OF THE ADMINISTRATOR.  Subject to the provisions of the 
Plan, and in the case of a Committee, subject to the specific duties 
delegated by the Board to such Committee, the Administrator shall have the 
authority, in its discretion:

               (i)    to determine the Fair Market Value of the Common Stock, 
in accordance with Section 2(m) of the Plan;

               (ii)   to select the Service Providers to whom Options may be 
granted hereunder;

               (iii)  to determine whether and to what extent Options are 
granted hereunder;

               (iv)   to determine the number of shares of Common Stock to be 
covered by each Option granted hereunder;

               (v)    to approve forms of agreement for use under the Plan;

               (vi)   to determine the terms and conditions, not inconsistent 
with the terms of the Plan, of any award granted hereunder.  Such terms and 
conditions include, but are not limited to, the exercise price, the time or 
times when Options may be exercised (which may be based on performance 
criteria), any vesting acceleration or waiver of forfeiture restrictions, and 
any restriction or limitation regarding any Option  or the shares of Common 
Stock relating thereto, based in each case on such factors as the 
Administrator, in its sole discretion, shall determine;

               (vii)  to reduce the exercise price of any Option to the then 
current Fair Market Value if the Fair Market Value of the Common Stock 
covered by such Option shall have declined since the date the Option was 
granted, provided that no such action shall be taken unless and until the 
approval of the Company's stockholders shall have been obtained;

               (viii) to institute an Option Exchange Program, provided that 
no such action shall be taken unless and until the approval of the Company's 
stockholders shall have been obtained;

               (ix)   to construe and interpret the terms of the Plan and 
awards granted pursuant to the Plan;

               (x)    to prescribe, amend and rescind rules and regulations 
relating to the Plan, including rules and regulations relating to sub-plans 
established for the purpose of qualifying for preferred tax treatment under 
foreign tax laws;

               (xi)   to modify or amend each Option (subject to Section 
15(b) of the Plan), including the discretionary authority to extend the 
post-termination exercisability period of Options longer than is otherwise 
provided for in the Plan;

                                       -4-



               (xii)  to authorize any person to execute on behalf of the 
Company any instrument required to effect the grant of an Option or  
previously granted by the Administrator;

               (xiii) to determine the terms and restrictions applicable to 
Options; 

               (xiv)  to allow Optionees to satisfy withholding tax 
obligations by electing to have the Company withhold from the Shares to be 
issued upon exercise of an Option or Stock Purchase Right that number of 
Shares having a Fair Market Value equal to the amount required to be 
withheld.  The Fair Market Value of the Shares to be withheld shall be 
determined on the date that the amount of tax to be withheld is to be 
determined.  All elections by an Optionee to have Shares withheld for this 
purpose shall be made in such form and under such conditions as the 
Administrator may deem necessary or advisable; and

               (xv)   to make all other determinations deemed necessary or 
advisable for administering the Plan.

          (d)  EFFECT OF ADMINISTRATOR'S DECISION.  The Administrator's 
decisions, determinations and interpretations shall be final and binding on 
all Optionees and any other holders of Options.

     5.   ELIGIBILITY.  Options may be granted to Service Providers.

     6.   LIMITATION.  Neither the Plan nor any Option shall confer upon an 
Optionee any right with respect to continuing the Optionee's relationship as 
a Service Provider with the Company, nor shall they interfere in any way with 
the Optionee's right or the Company's right to terminate such relationship at 
any time, with or without cause.

     7.   TERM OF PLAN.  The Plan shall become effective upon its adoption by 
the Board.  It shall continue in effect for ten (10) years, unless sooner 
terminated under Section 14 of the Plan. 

     8.   TERM OF OPTION.  The term of each Option shall be stated in the 
Option Agreement. 

     9.   OPTION EXERCISE PRICE AND CONSIDERATION.

          (a)  EXERCISE PRICE.  The per share exercise price for the Shares 
to be issued pursuant to exercise of an Option shall be determined by the 
Administrator.

          (b)  WAITING PERIOD AND EXERCISE DATES.  At the time an Option is 
granted, the Administrator shall fix the period within which the Option may 
be exercised and shall determine any conditions which must be satisfied 
before the Option may be exercised.

          (c)  FORM OF CONSIDERATION.  The Administrator shall determine the 
acceptable form of consideration for exercising an Option, including the 
method of payment.  Such consideration may consist entirely of:

                                       -5-



               (i)    cash;

               (ii)   check;

               (iii)  promissory note;

               (iv)   other Shares which (A) in the case of Shares acquired 
upon exercise of an option, have been owned by the Optionee for more than six 
months on the date of surrender, and (B) have a Fair Market Value on the date 
of surrender equal to the aggregate exercise price of the Shares as to which 
said Option shall be exercised;

               (v)    consideration received by the Company under a cashless 
exercise program implemented by the Company in connection with the Plan;

               (vi)   a reduction in the amount of any Company liability to 
the Optionee, including any liability attributable to the Optionee's 
participation in any Company-sponsored deferred compensation program or 
arrangement;

               (vii)  such other consideration and method of payment for the 
issuance of Shares to the extent permitted by Applicable Laws; or

               (viii) any combination of the foregoing methods of payment.

     10.  EXERCISE OF OPTION.

          (a)  PROCEDURE FOR EXERCISE; RIGHTS AS A SHAREHOLDER. Any Option 
granted hereunder shall be exercisable according to the terms of the Plan and 
at such times and under such conditions as determined by the Administrator 
and set forth in the Option Agreement.  An Option may not be exercised for a 
fraction of a Share.

               An Option shall be deemed exercised when the Company receives: 
(i) written or electronic notice of exercise (in accordance with the Option 
Agreement) from the person entitled to exercise the Option, and (ii) full 
payment for the Shares with respect to which the Option is exercised.  Full 
payment may consist of any consideration and method of payment authorized by 
the Administrator and permitted by the Option Agreement and the Plan.  Shares 
issued upon exercise of an Option shall be issued in the name of the Optionee 
or, if requested by the Optionee, in the name of the Optionee and his or her 
spouse. Until the Shares are issued (as evidenced by the appropriate entry on 
the books of the Company or of a duly authorized transfer agent of the 
Company), no right to vote or receive dividends or any other rights as a 
shareholder shall exist with respect to the Optioned Stock, notwithstanding 
the exercise of the Option. The Company shall issue (or cause to be issued) 
such Shares promptly after the Option is exercised.  No adjustment will be 
made for a dividend or other right for which the record date is prior to the 
date the Shares are issued, except as provided in Section 13 of the Plan.

                                       -6-



               Exercising an Option in any manner shall decrease the number 
of Shares thereafter available, both for purposes of the Plan and for sale 
under the Option, by the number of Shares as to which the Option is exercised.

          (b)  TERMINATION OF RELATIONSHIP AS A SERVICE PROVIDER.  If an 
Optionee ceases to be a Service Provider, other than upon the Optionee's 
death or Disability, the Optionee may exercise his or her Option, but only 
within such period of time as is specified in the Option Agreement, and only 
to the extent that the Option is vested on the date of termination (but in no 
event later than the expiration of the term of such Option as set forth in 
the Option Agreement). In the absence of a specified time in the Option 
Agreement, the Option shall remain exercisable for three (3) months following 
the Optionee's termination. If, on the date of termination, the Optionee is 
not vested as to his or her entire Option, the Shares covered by the unvested 
portion of the Option shall revert to the Plan.  If, after termination, the 
Optionee does not exercise his or her Option within the time specified by the 
Administrator, the Option shall terminate, and the Shares covered by such 
Option shall revert to the Plan.

          (c)  DISABILITY OF OPTIONEE.  If an Optionee ceases to be a Service 
Provider as a result of the Optionee's Disability, the Optionee may exercise 
his or her Option within such period of time as is specified in the Option 
Agreement, to the extent the Option is vested on the date of termination (but 
in no event later than the expiration of the term of such Option as set forth 
in the Option Agreement).  In the absence of a specified time in the Option 
Agreement, the Option shall remain exercisable for twelve (12) months 
following the Optionee's termination.  If, on the date of termination, the 
Optionee is not vested as to his or her entire Option, the Shares covered by 
the unvested portion of the Option shall revert to the Plan.  If, after 
termination, the Optionee does not exercise his or her Option within the time 
specified herein, the Option shall terminate, and the Shares covered by such 
Option shall revert to the Plan.

          (d)  DEATH OF OPTIONEE.  If an Optionee dies while a Service 
Provider, the Option may be exercised within such period of time as is 
specified in the Option Agreement (but in no event later than the expiration 
of the term of such Option as set forth in the Notice of Grant), by the 
Optionee's estate or by a person who acquires the right to exercise the 
Option by bequest or inheritance, but only to the extent that the Option is 
vested on the date of death.  In the absence of a specified time in the 
Option Agreement, the Option shall remain exercisable for twelve (12) months 
following the Optionee's termination.  If, at the time of death, the Optionee 
is not vested as to his or her entire Option, the Shares covered by the 
unvested portion of the Option shall immediately revert to the Plan.  The 
Option may be exercised by the executor or administrator of the Optionee's 
estate or, if none, by the person(s) entitled to exercise the Option under 
the Optionee's will or the laws of descent or distribution.  If the Option is 
not so exercised within the time specified herein, the Option shall 
terminate, and the Shares covered by such Option shall revert to the Plan.

          (e)  BUYOUT PROVISIONS.  The Administrator may at any time offer to 
buy out for a payment in cash or Shares, an Option previously granted based 
on such terms and conditions as the Administrator shall establish and 
communicate to the Optionee at the time that such offer is made.

                                       -7-



     11.  NON-TRANSFERABILITY OF OPTIONS .  Unless determined otherwise by 
the Administrator, an Option may not be sold, pledged, assigned, 
hypothecated, transferred, or disposed of in any manner other than by will or 
by the laws of descent or distribution and may be exercised, during the 
lifetime of the Optionee, only by the Optionee.  If the Administrator makes 
an Option transferable, such Option shall contain such additional terms and 
conditions as the Administrator deems appropriate.

     12.  ADJUSTMENTS UPON CHANGES IN CAPITALIZATION, DISSOLUTION, MERGER OR  
          ASSET SALE. 

          (a)  CHANGES IN CAPITALIZATION.  Subject to any required action by 
the shareholders of the Company, the number of shares of Common Stock covered 
by each outstanding Option, and the number of shares of Common Stock which 
have been authorized for issuance under the Plan but as to which no Options 
have yet been granted or which have been returned to the Plan upon 
cancellation or expiration of an Option, as well as the price per share of 
Common Stock covered by each such outstanding Option, shall be 
proportionately adjusted for any increase or decrease in the number of issued 
shares of Common Stock resulting from a stock split, reverse stock split, 
stock dividend, combination or reclassification of the Common Stock, or any 
other increase or decrease in the number of issued shares of Common Stock 
effected without receipt of consideration by the Company; provided, however, 
that conversion of any convertible securities of the Company shall not be 
deemed to have been "effected without receipt of consideration."  Such 
adjustment shall be made by the Board, whose determination in that respect 
shall be final, binding and conclusive. Except as expressly provided herein, 
no issuance by the Company of shares of stock of any class, or securities 
convertible into shares of stock of any class, shall affect, and no 
adjustment by reason thereof shall be made with respect to, the number or 
price of shares of Common Stock subject to an Option. 

          (b)  DISSOLUTION OR LIQUIDATION.  In the event of the proposed 
dissolution or liquidation of the Company, the Administrator shall notify 
each Optionee as soon as practicable prior to the effective date of such 
proposed transaction.  The Administrator in its discretion may provide for an 
Optionee to have the right to exercise his or her Option until ten (10) days 
prior to such transaction as to all of the Optioned Stock covered thereby, 
including Shares as to which the Option would not otherwise be exercisable.  
In addition, the Administrator may provide that any Company repurchase option 
applicable to any Shares purchased upon exercise of an Option shall lapse as 
to all such Shares, provided the proposed dissolution or liquidation takes 
place at the time and in the manner contemplated.  To the extent it has not 
been previously exercised, an Option will terminate immediately prior to the 
consummation of such proposed action.

          (c)  MERGER OR ASSET SALE.  In the event of a merger of the Company 
with or into another corporation, or the sale of substantially all of the 
assets of the Company, each outstanding Option shall be assumed or an 
equivalent option or right substituted by the successor corporation or a 
Parent or Subsidiary of the successor corporation.  In the event that the 
successor corporation refuses to assume or substitute for the Option, the 
Optionee shall fully vest in and have the right to exercise the Option as to 
all of the Optioned Stock, including Shares as to which it would not 
otherwise be vested or exercisable.  If an Option becomes fully vested and 
exercisable in lieu of assumption or substitution in the event of a merger or 
sale of assets, the Administrator shall notify the Optionee in 

                                       -8-



writing or electronically that the Option shall be fully vested and 
exercisable for a period of fifteen (15) days from the date of such notice, 
and the Option shall terminate upon the expiration of such period.  For the 
purposes of this paragraph, the Option shall be considered assumed if, 
following the merger or sale of assets, the option or right confers the right 
to purchase or receive, for each Share of Optioned Stock, immediately prior 
to the merger or sale of assets, the consideration (whether stock, cash, or 
other securities or property) received in the merger or sale of assets by 
holders of Common Stock for each Share held on the effective date of the 
transaction (and if holders were offered a choice of consideration, the type 
of consideration chosen by the holders of a majority of the outstanding 
Shares); provided, however, that if such consideration received in the merger 
or sale of assets is not solely common stock of the successor corporation or 
its Parent, the Administrator may, with the consent of the successor 
corporation, provide for the consideration to be received upon the exercise 
of the Option, for each Share of Optioned Stock to be solely common stock of 
the successor corporation or its Parent equal in fair market value to the per 
share consideration received by holders of Common Stock in the merger or sale 
of assets.

     13.  DATE OF GRANT.  The date of grant of an Option shall be, for all 
purposes, the date on which the Administrator makes the determination 
granting such Option, or such other later date as is determined by the 
Administrator. Notice of the determination shall be provided to each Optionee 
within a reasonable time after the date of such grant.

     14.  AMENDMENT AND TERMINATION OF THE PLAN.

          (a)  AMENDMENT AND TERMINATION.  The Board may at any time amend, 
alter, suspend or terminate the Plan.  

          (b)  EFFECT OF AMENDMENT OR TERMINATION.  No amendment, alteration, 
suspension or termination of the Plan shall impair the rights of any 
Optionee, unless mutually agreed otherwise between the Optionee and the 
Administrator, which agreement must be in writing and signed by the Optionee 
and the Company. Termination of the Plan shall not affect the Administrator's 
ability to exercise the powers granted to it hereunder with respect to 
options granted under the Plan prior to the date of such termination.

     15.  CONDITIONS UPON ISSUANCE OF SHARES.  

          (a)  LEGAL COMPLIANCE.  Shares shall not be issued pursuant to the 
exercise of an Option unless the exercise of such Option and the issuance and 
delivery of such Shares shall comply with Applicable Laws and shall be 
further subject to the approval of counsel for the Company with respect to 
such compliance.

          (b)  INVESTMENT REPRESENTATIONS.  As a condition to the exercise of 
an Option the Company may require the person exercising such Option  to 
represent and warrant at the time of any such exercise that the Shares are 
being purchased only for investment and without any present 

                                       -9-



intention to sell or distribute such Shares if, in the opinion of counsel for 
the Company, such a representation is required.

     16.  INABILITY TO OBTAIN AUTHORITY.  The inability of the Company to 
obtain authority from any regulatory body having jurisdiction, which 
authority is deemed by the Company's counsel to be necessary to the lawful 
issuance and sale of any Shares hereunder, 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.

     17.  RESERVATION OF SHARES.  The Company, during the term of this Plan, 
will at all times reserve and keep available such number of Shares as shall 
be sufficient to satisfy the requirements of the Plan.

                                       -10-