<PAGE>

                                                                    EXHIBIT 10.1
 
                                AMENDMENT NO. 1
                                      TO
                               AXON CORPORATION
                            1990 STOCK OPTION PLAN


     The Axon Corporation l990 Stock Option Plan (the "Plan") is hereby amended
as follows:

     1.   Section 3 of the Plan is amended to read as follows:

               SECTION 3.  Stock Subject to this Plan. The stock subject to this
                           --------------------------                       
            Plan shall be the Company's Common Stock (the "Common Stock")
            presently authorized but unissued or subsequently acquired by the
            Company. Subject to adjustment as provided in Section 7 hereof, the
            aggregate amount of Common Stock to be delivered upon the exercise
            of all options granted under this Plan shall not exceed Six Hundred
            Fifty Thousand (650,000) shares as such Common Stock was constituted
            on the effective date of Amendment No. 1 to this Plan. If any option
            granted under this Plan shall expire, be surrendered, exchanged for
            another option, cancelled or terminated for any reason without
            having been exercised in full, the unpurchased shares subject
            thereto shall thereupon again be available for purposes of this
            Plan, including for replacement options which may be granted in
            exchange for such surrendered, cancelled or terminated options.

     The effective date of such amendment shall be April 2, 1991, the date of
                                                   -------
adoption by the Board, unless the shareholders of the corporation fail to
approve such amendment within twelve months before or after the date of adoption
by the Board of Directors.




28481
<PAGE>
 
                                AMENDMENT NO. 2
                                      TO
                               AXON CORPORATION
                            1990 STOCK OPTION PLAN


     The Axon Corporation l990 Stock Option Plan (the "Plan") is hereby amended
as follows:

     1.   Section 3 of the Plan is amended to read as follows:

               SECTION 3.  Stock Subject to this Plan. The stock subject to this
                           --------------------------
            Plan shall be the Company's Common Stock (the "Common Stock")
            presently authorized but unissued or subsequently acquired by the
            Company. Subject to adjustment as provided in Section 7 hereof, the
            aggregate amount of Common Stock to be delivered upon the exercise
            of all options granted under this Plan shall not exceed Seven
            Hundred Ten Thousand (710,000) shares as such Common Stock was
            constituted on the effective date of Amendment No. 2 to this Plan.
            If any option granted under this Plan shall expire, be surrendered,
            exchanged for another option, cancelled or terminated for any reason
            without having been exercised in full, the unpurchased shares
            subject thereto shall thereupon again be available for purposes of
            this Plan, including for replacement options which may be granted in
            exchange for such surrendered, cancelled or terminated options.

     The effective date of such amendment shall be April 10, 1991, the date of
                                                   --------
adoption by the Board, unless the shareholders of the corporation fail to
approve such amendment within twelve months before or after the date of adoption
by the Board of Directors.



 
28481
<PAGE>
 
                                AMENDMENT NO. 3
                                      TO
                               AXON CORPORATION
                            1990 STOCK OPTION PLAN


     The Axon Corporation l990 Stock Option Plan (the "Plan") is hereby amended
as follows:

     1.   Section 3 of the Plan is amended to read as follows:

               SECTION 3.  Stock Subject to this Plan. The stock subject to this
                           --------------------------
            Plan shall be the Company's Common Stock (the "Common Stock")
            presently authorized but unissued or subsequently acquired by the
            Company. Subject to adjustment as provided in Section 7 hereof, the
            aggregate amount of Common Stock to be delivered upon the exercise
            of all options granted under this Plan shall not exceed Nine Hundred
            Sixty Thousand (960,000) shares as such Common Stock was constituted
            on the effective date of Amendment No. 3 to this Plan. If any option
            granted under this Plan shall expire, be surrendered, exchanged for
            another option, cancelled or terminated for any reason without
            having been exercised in full, the unpurchased shares subject
            thereto shall thereupon again be available for purposes of this
            Plan, including for replacement options which may be granted in
            exchange for such surrendered, cancelled or terminated options.

     The effective date of such amendment shall be February 19, 1992, the date
of adoption by the Board, unless the shareholders of the corporation fail to
approve such amendment within twelve months before or after the date of adoption
by the Board of Directors.
<PAGE>
 
                                AMENDMENT NO. 4
                                      TO
                               AXON CORPORATION
                            1990 STOCK OPTION PLAN


     The Axon Corporation l990 Stock Option Plan (the "Plan") is hereby amended
as follows:

     1.   Section 3 of the Plan is amended to read as follows:

               SECTION 3.  Stock Subject to this Plan. The stock subject to this
                           --------------------------                           
            Plan shall be the Company's Common Stock (the "Common Stock")
            presently authorized but unissued or subsequently acquired by the
            Company. Subject to adjustment as provided in Section 7 hereof, the
            aggregate amount of Common Stock to be delivered upon the exercise
            of all options granted under this Plan shall not exceed One Million
            Sixty Thousand (1,060,000) shares as such Common Stock was
            constituted on the effective date of Amendment No. 4 to this Plan.
            If any option granted under this Plan shall expire, be surrendered,
            exchanged for another option, cancelled or terminated for any reason
            without having been exercised in full, the unpurchased shares
            subject thereto shall thereupon again be available for purposes of
            this Plan, including for replacement options which may be granted in
            exchange for such surrendered, cancelled or terminated options.

     The effective date of such amendment shall be June 30, 1992, the date of
adoption by the Board, unless the shareholders of the corporation fail to
approve such amendment within twelve months before or after the date of adoption
by the Board of Directors.
<PAGE>
 
                                AMENDMENT NO. 5
                                      TO
                               AXON CORPORATION
                            1990 STOCK OPTION PLAN


     The Axon Corporation l990 Stock Option Plan (the "Plan") is hereby amended
as follows:


     1.   Section 1 of the Plan is amended to read as follows:


                 SECTION 1.   Purpose. The purpose of the Shapeware Corporation
                              -------                                          
            1990 Stock Option Plan (the "Plan") is to provide a means whereby
            selected employees, directors (subject to the restrictions contained
            in Sections 2 and 4), officers, agents, consultants and independent
            contractors of Shapeware Corporation (the "Company") or of any
            parent or subsidiary (as defined in subsection 5.7 and referred to
            hereinafter as "related corporations") thereof, may be granted
            incentive stock options and/or nonqualified stock options to
            purchase the Common Stock (as defined in Section 3) of the Company,
            in order to attract and retain the services or advice of such
            employees, directors, offices, agents, consultants and independent
            contractors and to provide added incentive to them by encouraging
            stock ownership in the Company.


The effective date of such amendment shall be July 24, 1992, the date of
adoption by the Board of Directors.
<PAGE>
 
                                AMENDMENT NO. 6
                                      TO
                               AXON CORPORATION
                            1990 STOCK OPTION PLAN


     The Axon Corporation l990 Stock Option Plan (the "Plan") is hereby amended
as follows:


     1.   Section 3 of the Plan is amended to read as follows:


                 "SECTION 3.  Stock Subject to this Plan. The stock subject to
                              --------------------------                      
            this Plan shall be the Company's Common Stock (the "Common Stock")
            presently authorized but unissued or subsequently acquired by the
            Company. Subject to adjustment as provided in Section 7 hereof, the
            aggregate amount of Common Stock to be delivered upon the exercise
            of all options granted under this Plan shall not exceed One Million
            Three Hundred Ten Thousand (1,310,000) shares as such Common Stock
            was constituted on the effective date of Amendment No. 6 to this
            Plan. If any option granted under this Plan shall expire, be
            surrendered, exchanged for another option, cancelled or terminated
            for any reason without having been exercised in full, the
            unpurchased shares subject thereto shall thereupon again be
            available for purposes of this Plan, including for replacement
            options which may be granted in exchange for such surrendered,
            cancelled or terminated options."


     The effective date of such amendment shall be March 22, 1993, the date of
adoption by the Board, unless the shareholders of the corporation fail to
approve such amendment within twelve months before or after the date of adoption
by the Board of Directors.
<PAGE>
 
                                AMENDMENT NO. 7
                                      TO
                               AXON CORPORATION
                            1990 STOCK OPTION PLAN


     Section 5.13 of the Shapeware Corporation 1990 Stock Option Plan (the
"Plan") is hereby amended to read as follows:


             "5.13 Stock Restriction Agreement.   Notwithstanding the provisions
                   ---------------------------                                  
     of Section 5.2 or the option agreement evidencing an option regarding the
     time or times at which an option becomes exercisable, an option shall
     become exercisable immediately upon execution by the optionee of a Stock
     Restriction Agreement in the form attached to the Plan as Exhibit 1."


     The effective date of such amendment, shall be January 4, 1994, the date of
adoption by the Board of Directors.
<PAGE>
 
                                AMENDMENT NO. 8
                                       TO
                             SHAPEWARE CORPORATION
                             1990 STOCK OPTION PLAN



     Section 3 of the Shapeware Corporation 1990 Stock Option Plan (the "Plan")
is hereby amended to read as follows:

               "SECTION 3. Stock Subject to this Plan. The stock subject to this
                           --------------------------
          Plan shall be the Company's Common Stock (the "Common Stock")
          presently authorized but unissued or subsequently acquired by the
          Company. Subject to adjustment as provided in Section 7 hereof, the
          aggregate amount of Common Stock to be delivered upon the exercise of
          all options granted under this Plan shall not exceed Two Million Three
          Hundred Ten Thousand (2,310,000) shares as such Common Stock was
          constituted on the effective date of Amendment No. 8 to this Plan. If
          any option granted under this Plan shall expire, be surrendered,
          exchanged for another option, cancelled or terminated for any reason
          without having been exercised in full, the unpurchased shares subject
          thereto shall thereupon again be available for purposes of this Plan,
          including for replacement options which may be granted in exchange for
          such surrendered, cancelled or terminated options."


     The effective date of such amendment shall be January 19, 1994, the date of
adoption by the Board of Directors.

                                      -1-
<PAGE>
 
                                AMENDMENT NO. 9
                                       TO
                               VISIO CORPORATION
             (formerly Shapeware Corporation and Axon Corporation)

                             1990 STOCK OPTION PLAN


     Section 1 of the Visio Corporation 1990 Stock Option Plan (the "Plan") is
hereby amended to read as follows:


             "SECTION 1. Purpose. The purpose of the Visio Corporation 1990
                         -------
         Stock Option Plan (this "Plan") is to provide a means whereby selected
         employees, directors (subject to restrictions contained in Sections 2
         and 4), officers, agents, consultants and independent contractors of
         Visio Corporation (the "Company") or of any parent or subsidiary (as
         defined in subsection 5.7 and referred to hereinafter as "related
         corporations") thereof, may be granted incentive stock options and/or
         nonqualified stock options to purchase the Common Stock (as defined in
         Section 3) of the Company, in order to attract and retain the services
         or advice of such employees, directors, officers, agents, consultants
         and independent contractors and to provide added incentive to them by
         encouraging stock ownership in the Company."

     The effective date of the amendment shall be July 27, 1995, the date of
adoption by the Board of Directors.
<PAGE>
 
                                AMENDMENT NO. 10

                                     TO THE

                               VISIO CORPORATION

                             1990 STOCK OPTION PLAN

                                        

     The Visio Corporation (formerly Axon Corporation and Shapeware Corporation)
1990 Stock Option Plan (the "Plan") is hereby amended as follows:


     1.  The first two paragraphs of Section 2 of the Plan shall be amended in
their entirety to read as follows:


               Administration.  This Plan shall be administered by the Board of
               --------------                                                  
          Directors of the Company (the "Board") or a committee or committees
          (which term includes subcommittees) appointed by, and consisting of
          two or more members of, the Board.  The administrator of this Plan
          shall hereinafter be referred to as the "Plan Administrator."  If and
          so long as the Common Stock is registered under Section 12(b) or 12(g)
          of the Securities Exchange Act of 1934, as amended (the "Exchange
          Act"), the Board shall consider, in selecting the Plan Administrator
          and the membership of any committee acting as Plan Administrator of
          the Plan with respect to any persons subject or likely to become
          subject to Section 16 under the Exchange Act, the provisions regarding
          (a) "outside directors," as contemplated by Section 162(m) of the
          Internal Revenue Code of 1986, as amended (the "Code"), and (b)
          "nonemployee directors," as contemplated by Rule 16b-3 under the
          Exchange Act.  The Board may delegate the responsibility for
          administering this Plan with respect to designated classes of eligible
          participants to different committees, subject to such limitations as
          the Board deems appropriate.  Committee members shall serve for such
          term as the Board may determine, subject to removal by the Board at
          any time.


     2.  The first sentence of Section 2.3 shall be deleted.

     3.  Section 5.6 shall be amended in its entirety to read:


               5.6  Transferability.  No Option, Stock Appreciation Right,
                    ---------------                                       
          Performance Award or Other Stock-Based Award granted under the 
<PAGE>
 
          Plan may be assigned, pledged or transferred by the Holder other than
          by will or by the laws of descent and distribution and, during the
          Holder's lifetime, such Awards may be exercised only by the Holder or
          a permitted assignee or transferee of the Holder (as provided below).
          Notwithstanding the foregoing, and to the extent permitted by Section
          422 of the Code, the Plan Administrator, in its sole discretion, may
          permit such assignment, transfer and exercisability and may permit a
          Holder of such Awards to designate a beneficiary who may exercise the
          Award or receive compensation under the Award after the Holder's
          death; provided, however, that any such Award so assigned, pledged or
          transferred shall be subject to all the same terms and conditions
          contained in the instrument evidencing the award.


     4.  The following sentence shall be inserted at the beginning of Section
5.7:

               If the Optionee's relationship with the Company or any related
          corporation ceases for any reason, then the portion of the Optionee's
          option which is not exercisable at the time of such cessation shall
          terminate immediately upon such cessation, unless the Plan
          Administrator determines otherwise.


     The effective date of such amendments shall be ____________, 1996.

                                      -2-
<PAGE>
 
                               AXON CORPORATION

                            1990 STOCK OPTION PLAN


     Section 1.   Purpose.   The purpose of the Axon Corporation 1990 Stock
                  -------                                                  
Option Plan (this "Plan") is to provide a means whereby selected employees,
directors (subject to the restrictions contained in Sections 2 and 4), officers,
agents, consultants and independent contractors of Axon Corporation (the
"Company") or of any parent or subsidiary (as defined in subsection 5.7 and
referred to hereinafter as "related corporations") thereof, may be granted
incentive stock options and/or nonqualified stock options to purchase the Common
Stock (as defined in Section 3) of the Company, in order to attract and retain
the services or advice of such employees, directors, officers, agents ,
consultants and independent contractors and to provide added incentive to them
by encouraging stock ownership in the Company.

     Section 2.   Administration.   This Plan shall be administered by the Board
                  --------------                                                
of Directors of the Company (the "Board") or, in the event the Board shall
appoint and/or authorize a committee to administer this Plan, by such committee.
The administrator of this Plan shall hereinafter be referred to as the "Plan
Administrator."

     The foregoing notwithstanding, in the event the Company shall register any
of its equity securities pursuant to Section 12 (b) or 12 (g) of the Securities
Exchange Act of 1934, as amended (the "Exchange Act"), and any directors are
eligible to receive options under this Plan, then the following provisions shall
apply to the administration of the Plan with respect to grants made to
directors. The Plan Administrator shall be constituted at all times so as to
meet the requirements of Section 16 (b) of the Exchange Act, as amended from
time to time. Currently, the Plan Administrator shall be the Board, a majority
of which Board and a majority of which directors acting in the matter are
disinterested, or may be a committee which consists solely of not less than
three disinterested directors of the Company. In the event the Plan
Administrator is a committee and state corporate law does not permit a committee
to grant options to directors, then directors shall not be eligible to receive
options under this Plan as any committee serving as Plan Administrator shall be
appointed by the Board for such term as the Board may determine. The Board may
from time to time remove members from, or add members to, the committee.
Vacancies on the committee, however caused, may be filled by the Board. If at
any time an insufficient number of disinterested directors is available to serve
on such committee, interested directors may serve on the committee; however,
during such time, no options shall be granted under this Plan to any person if
the granting of such option would not meet the requirements of Section 16(b) of
the Exchange Act.

                                       1
<PAGE>
 
     For purposes of this Section 2, a disinterested director is a member of the
Board who meets the definition of "disinterested person" as set forth in the
rules and regulations promulgated under Section 16 (b) of the Exchange Act, as
amended from time to time.  Currently, a disinterested director for purposes of
this Section 2 is a member of the Board who is not at the time he or she
exercises discretion in administering this Plan eligible and has not been
eligible at any time within one year prior thereto (or since the effective date
of the Company's registration under Section 12 (b) or 12 (g) of the Exchange Act
if the Company has been registered for less than 12 months) for selection as a
person to whom stock may be allocated or to whom stock options or stock
appreciation rights may be granted pursuant to this Plan or any other
discretionary plan of the Company or any related corporation entitling the
participants therein to acquire stock, stock options, or stock appreciation
rights of the Company or any related corporation.

          2.1   Procedures.   The Board shall designate one of the members of
                ----------                                                   
the Plan Administrator as chairman.  The Plan Administrator may hold meetings at
such times and places as it shall determine.  The acts of majority of the
members of the Plan Administrator present at meetings at which a quorum
Administrator members, shall be valid acts of the Plan.

          2.2    Responsibilities.   Except for the terms and conditions
                 ----------------                                       
explicitly set forth in this Plan, the Plan Administrator shall have the
authority, in its discretion, to determine all matters relating to the options
to be granted under this Plan, including selection of the individuals to be
granted options, the number of shares to be subject to each of the options.
Grants under this Plan need not be identical in any respect, even when made
simultaneously.  The interpretation and construction by the Plan Administrator
of any terms or provisions of this Plan or any option issued hereunder, or of
any rule or regulation promulgated in connection herewith, shall be conclusive
and binding on all interested parties, so long as such interpretation and
construction with respect to incentive stock options correspond to the
requirements of Internal Revenue Code (the "Code") Section 422A, the regulations
thereunder, and any amendments thereto.

          2.3   Section 16(b) Compliance and Bifurcation of Plan.   It is the
                ------------------------------------------------             
intention of the Company that this Plan comply in all respects with Rule 16b-3
under the Exchange Act and, if any Plan provision is later found not to be in
compliance with such Section, the provision shall be deemed null and void, and
in the Plan to the contrary, the Board, in its absolute discretion, may
bifurcate the Plan so as to restrict, limit or condition the use of any
provisions of the Plan to participants who are officers and directors subject to
Section 16(b) of the Exchange Act without so restricting, limiting or
conditioning the Plan with respect to other participants.

     SECTION 3.  Stock Subject to This Plan.   The stock subject to this Plan
                 --------------------------                                  
shall be the Company's common Stock (the "Common Stock") presently authorized by
unissued or subsequently acquired by the Company.  Subject to adjustment as
provided in Section 7 hereof, the aggregate amount of Common Stock to be
delivered upon the exercise of all 

                                       2
<PAGE>
 
options granted under this Plan shall not exceed 500,000 shares as such Common
Stock was constituted on the effective date of this Plan. If any option granted
under this Plan shall expire, be surrendered, exchanged for another option,
cancelled or terminated for any reason without having been exercised in full,
the unpurchased shares subject thereto shall thereupon again be available for
purposes of this Plan, including for replacement options which may be granted in
exchange for such surrendered, cancelled or terminated options.

     SECTION 4.   Eligibility.   An incentive stock option may be granted only
                  -----------                                                 
to any individual who, at the time the option is granted, is an employee of the
Company or any related corporation.  A nonqualified stock option may be granted
to any employee, director, officer, agent, consultant or independent contractor
of the Company or any related corporation., whether an individual or an entity.
The members of the Board who are not also employees of the Company shall not be
eligible to receive options under this Plan once the Company has registered any
of its equity securities pursuant to Section 12(b) or 12(g) of the Exchange Act.
Any party to whom an option is granted under this Plan shall be referred to
hereinafter as an "Optionee."

     SECTION 5.   Terms and Conditions of Options.   Options granted under this
                  -------------------------------                              
Plan shall be evidenced by written agreements which shall contain such terms,
conditions, limitations and restrictions as the Plan Administrator shall deem
advisable and which are not inconsistent with this Plan. Notwithstanding the
foregoing, options shall include or incorporate by reference the following terms
and conditions.


          5.1   Number of Shares and Price.   The maximum number of shares that
                --------------------------                                     
may be purchased pursuant to the exercise of each option and the price per share
at which such option is exercisable (the "exercise price") shall be as
established by the Plan Administrator, provided that the Plan Administrator
shall act in good faith to establish the exercise price which shall be not less
than the fair market value per share on the Common Stock at the time the option
is granted with respect to incentive stock options an, after the Company has
registered any of its equity securities pursuant to Section 12(b) or 12(g) of
the Exchange act, not less than 85% of the fair market value per share of the
common Stock at the time the options is granted with respect to nonqualified
stock options and also provided that, with respect to incentive stock options
granted to greater than 10% shareholders, the exercise price shall be as
required by Section 6.

          5.2   Term and Maturity.   Subject to the restrictions contained in
                -----------------                                            
Section 6 with respect to granting incentive stock options to greater than 10%
shareholders, the term of each incentive stock option shall be as established by
the Plan Administrator and, if not so established, shall be 10 years from the
date it is granted but in no event shall the term of any incentive stock option
exceed 10 years. The term of each nonqualified stock option shall be as
established by the Plan Administrator, and if not so established, shall be 10
years. To ensure that the Company or related corporation will achieve the
purpose and receive the benefits contemplated in this Plan, any option granted
to any Optionee hereunder shall, unless the condition of this sentence is waived
or modified in the 

                                       3
<PAGE>
 
agreement evidencing the option or by resolution adopted by the Plan
Administrator, be exercisable according to the following schedule:

<TABLE>
<CAPTION>
          Period of Optionee's 
      Continuous Relationship With  
        the Company or a Related 
          Corporation From the                   Portion of Total Option
        Date the Option is Granted                 Which is Exercisable
     ------------------------------             -------------------------
      <S>                                        <C>
             After one year                                 25%

      After each three-month period                An additional 6.25%
          completed thereafter
 
             After 4 years                                  100%
</TABLE>



          5.3   Exercise.   Subject to the vesting schedule described in
                --------                                                
subsection 5.2 above and to any additional holding period required by applicable
law, each option may be exercised in whole or in part; provided, however, that
no fewer than 50 shares (or the remaining shares then purchasable under the
option, if less than 50 shares) may be purchased upon any exercise of option
rights hereunder and the only whole shares will be issued pursuant to the
exercise of any option.  During an Optionee's lifetime, any incentive stock
options granted under this Plan are personal to him or her and are exercisable
solely by such Optionee.  Options shall be exercised by delivery to the Company
of Notice of the number of shares with respect to which the option is exercised,
together with payment of the exercise price.

          5.4   Payment of Exercise Price.   Payment of the option exercise
               --------------------------                                  
price shall be made in full at the time the notice of exercise of the option is
delivered to the Company and shall be in cash, bank certified or cashier's check
or personal check (unless at the time of exercise the Plan Administrator in a
particular case determines not to accept a personal check) for the Common Stock
being purchased.


     The Plan Administrator can determine at the time the option is granted for
incentive stock options, or at any time before exercise for nonqualified stock
options, that additional forms of payment will be permitted,  To the extent
permitted by the Plan Administrator and applicable laws and regulations
(including, but not limited to, federal tax and securities laws and regulations
and state corporate law), an option may be exercised by:


          (a) delivery of shares of stock of the Company held by and Optionee
having a fair market value equal to the exercise price, such fair market value
to be determined in good faith by the Plan Administrator; provided, however,
that payment

                                       4
<PAGE>
 
in stock held by an Optionee shall not be made unless the stock shall have been
owned by the Optionee for a period of at least six months;

          (b) delivery of a full-recourse promissory note executed by the
Optionee; provided that (i) such note delivered in connection with an incentive
stock option shall, and such note delivered in connection with a nonqualified
stock option may, in the sole discretion of the Plan Administrator, bear
interest at a rate specified by the Plan Administrator but in no case less than
the rate required to avoid imputation of interest (taking into account any
exceptions to the inputed interest rules) for federal income tax purposes, and
(ii) the Plan Administrator in its sole discretion shall specify the term and
other provisions of such note at the time an incentive stock option is granted
or at any time prior to exercise of a nonqualified stock option, and (iii) the
Plan Administrator may require that the Optionee pledge the Optionee's shares to
the Company for the purpose of securing the payment of such note and may require
that the certificate representing such shares be held in escrow in order to
perfect the Company's security interest, and (iv) the Plan Administrator in its
sole discretion may at any time restrict or rescind this right upon notification
to the Optionee; or

          (c) delivery of a properly executed exercise notice, together with
irrevocable instructions to a broker, all in accordance with the regulations of
the Federal Reserve Board, to promptly deliver to the Company the amount of sale
or loan proceeds to pay the exercise price and any federal, state or local
withholding tax obligations that may arise in connection with the exercise;
provided, that the Plan Administrator, in its sole discretion, ,may at any time
determine that this subparagraph (c), to the extent the instructions to the
broker call for an immediate sale of the shares, shall not be applicable to any
Optionee who is subject to Section 16(b) of the Exchange Act if such transaction
would be in violation of Section 16(b), or is not an employee at the time of
exercise.

          5.5  Withholding Tax Requirement. The Company or related
               ---------------------------                          
corporation shall have the right to retain and withhold from any payment of cash
or Common Stock under the plan the amount of taxes required by any government to
be withheld or otherwise deducted and paid with respect to such payment. At its
discretion, the Company may require an Optionee receiving shares of Common Stock
to reimburse the Company for any such taxes required to be withheld by the
Company and withhold any distribution in whole or in part until the Company is
so reimbursed. In lieu thereof, the Company shall have the right to withhold
from any other cash amounts due or to become due from the Company to the
Optionee an amount equal to such taxes or retain and withhold a number of shares
having a market value not less than the amount of such taxes required to be
withheld by the Company to reimburse the Company for any such taxes and cancel
(in whole or in part) any such shares so withheld. If required by Section 16(b)
of the Exchange Act, the election to pay withholding taxes by delivery of shares
held by any person who at the time of exercise is subject to Section 16(b) of
the Exchange Act, shall be made either by six months prior to the date the
option exercise becomes taxable or during the quarterly 10-day window period
required under Section 16(b) of the Exchange Act for exercises of stock
appreciation rights.

                                       5
<PAGE>
 
          5.6  Nontransferability of Options.   Options granted under this Plan
               -----------------------------                                   
and the rights and privileges conferred hereby may not be transferred, assigned,
pledged or hypothecated in any manner (whether by operation of law or otherwise)
other than by will or by the applicable laws of descent and distribution, and
shall not be subject to execution, attachment or similar process. Any attempt to
transfer. assign, pledge, hypothecate or otherwise dispose of any option under
this Plan or of any right or privilege conferred hereby, contrary to the Code or
to the provisions of this Plan, or the sale or levy or any attachment or similar
process upon the rights and privileges conferred hereby shall be null and void.
Notwithstanding the foregoing, an Optionee may during the Optionee's lifetime,
designate a person who may exercise the option after the Optionee's death by
giving written notice of such designation to the Plan Administrator. Such
designation may be changed from time to time by the Optionee by giving written
notice to the Plan Administrator revoking any earlier designation and making a
new designation.

          5.7  Termination of Relationship.  If the Optionee's relationship
               ---------------------------                                 
with the Company or any related corporation ceases for any reason other than
termination for cause, death or total disability, and unless by its terms the
option sooner terminates or expires, then the Optionee may exercise, for a 
three-month period, that portion of the Optionee's option which is exercisable
at the time of such ce6sation, but the Optionee's option shall terminate at the
end of the three-month period following such cessation as to all shares for
which it has not theretofore been exercised unless this provision is waived in
the agreement evidencing the option or by resolution adopted by the Plan
Administrator, Incentive stock options not exercised within three months after
cessation of employment will no longer qualify as incentive stock options under
the Code. If, in the case of an incentive stock option, an Optionee's
relationship with the Company or related corporation changes (i.e., from
employee to nonemployee, such as a consultant), such change shall constitute a
termination of an Optionee's employment with the Company or related corporation
and the Optionee's incentive stock option shall terminate in accordance with
this subsection 5.7.

     If an Optionee is terminated for cause, any option granted hereunder shall
automatically terminate as of the first discovery by the Company of any reason
for termination for cause, and such Optionee shall thereupon have no right to
purchase any shares pursuant to such option. "Termination for cause" shall mean
dismissal for dishonesty, conviction or confession of a crime punishable by law
(except minor violations), fraud, misconduct or disclosure of confidential
information. If an Optionee's relationship with the Company or any related
corporation is suspended pending an investigation of whether or not the Optionee
shall be terminated for cause, all Optionee's rights under any option granted
hereunder likewise shall be suspended during the period of investigation.

     If an Optionee's relationship with the Company or any related corporation
ceases because of a total disability, the Optionee's option shall not terminate
or, in the case of an 

                                       6
<PAGE>
 
incentive stock option, cease to be treated as an incentive stock option until
the end of the 12-month period following such cessation (unless by its terms it
sooner terminates and expires). As used in this Plan, the term "total
disability" refers to a mental or physical impairment of the Optionee which is
expected to result in death or which has lasted or is expected to last for a
continuous period of 12 months or more and which causes the Optionee to be
unable, in the opinion of the Company and two independent physicians, to perform
his or her duties for the Company and to be engaged in any substantial gainful
activity. Total disability shall be deemed to have occurred on the first day
after the Company and the two independent physicians have furnished their
opinion of total disability to the Plan Administrator.

     For purposes of this subsection 5.7, a transfer of relationship between or
among the Company and/or any related corporation shall not be deemed to
constitute a cessation of relationship with the Company or any of its related
corporations. For purposes of this subsection 5. 7, with respect to incentive
stock options, employment shall be deemed to continue while the Optionee is on
military leave, sick leave or other bona fide leave of absence (as determined by
the Plan Administrator). The foregoing notwithstanding, employment shall not be
deemed to continue beyond the first 90 days of such leave, unless the Optionee's
reemployment rights are guaranteed by statute or by contract.

     As used herein, the term "related corporation," when referring to a
subsidiary corporation, shall mean any corporation (other than the company) in,
at the time of the granting of the option, an unbroken chain of corporations
ending with the company, if stock possessing 50% or more of the total combined
voting power of all classes of stock of each of the corporations other than the
Company is owned by one of the other corporations in such chain. When referring
to a parent corporation, the term "related corporation" shall mean any
corporation in an unbroken chain of corporations ending with the Company if, at
the time of the granting of the option, each of the corporations other than the
Company owns stock possessing 50% or more of the total combined voting power of
all classes of stock in one of the other corporations in such chain.

          5.8   Death of Optionee.    If an optionee dies while he or she has a
                -----------------                                              
relationship with the Company or any related corporation or within the three-
month period (or 12-month period in the case of totally disabled optionees)
following cessation of such relationship, any option held by such Optionee to
the extent that the Optionee would have been entitled to exercise such option,
may be exercised within 12 months after his or her death by the personal
representative of his or her estate or by the person or persons to whom the
Optionee's rights under the option shall pass by will or by the applicable laws
of descent and distribution.

          5.9   Status of Shareholder.  Neither the Optionee nor any party to
                ---------------------                                        
which the Optionee's rights and privileges under the option may pass shall be.
or have any of the rights or privileges of, a shareholder of the Company with
respect to any of the shares issuable upon the exercise of any option granted
under this Plan unless and until such option has been exercised.

                                       7
<PAGE>
 
          5.10  Contribution of Employment.   Nothing in this Plan or in any
                --------------------------                                  
option granted pursuant to this Plan shall confer upon any Optionee any right to
continue in the employ of the Company or of a related corporation, or to
interfere in any way with the right of the Company or of any such related
corporation to terminate his or her employment or other relationship with the
Company at any time.

          5.11  Modification and Amendment of Option.  Subject to the
                ------------------------------------                 
requirements of Code Section 422A with respect to incentive stock options and to
the terms and conditions and within the limitations of this Plan, the Plan
Administrator may modify or amend outstanding options granted under this Plan.
The modification or amendment of an outstanding option shall not, without the
consent of the Optionee, impair or diminish any of his or her rights or any of
the obligations of the Company under such option. Except as otherwise provided
in this Plan, no outstanding option shall be terminated without the consent of
the Optionee. Unless the Optionee agrees otherwise, any changes or adjustments
made to outstanding incentive stock options  granted under this Plan shall be
made in such a manner so as not to constitute a "modification" as defined in
Code Section 425(h) and so as not to cause any incentive stock option issued
hereunder to fail to continue to qualify as an incentive stock option as defined
in Code Section 422(b).

          5.12   Limitation on Value for Incentive Stock Options.   As to all
                 -----------------------------------------------             
incentive stock options granted under the terms of this Plan, to the extent that
the aggregate fair market value (determined at the time the incentive stock
option is granted) of the stock with respect to which incentive stock options
are exercisable for the first time by the Optionee during any calendar year
(under this Plan and all other incentive stock option plans of the Company, a
related corporation or a predecessor corporation) exceeds $100,000, such options
shall be treated as nonqualified stock options. The previous sentence shall not
apply if the Internal Revenue Service publicly rules, issues a private ruling to
the Company, any Optionee, or any legatee, personal representative or
distributee of an Optionee or issues regulations changing or eliminating such
annual limit.


     SECTION 6.   Greater Than 10% Shareholders.
                  ----------------------------- 

          6.1  Exercise Price and Term of Incentive Stock Options.  If incentive
               --------------------------------------------------               
stock options are granted under this Plan to employees who own more than 10% of
the total combined voting power of all classes of stock of the Company or any
related corporation, the term of such incentive stock options shall not exceed
five years and the exercise price shall be not less than 110% of the fair market
value of the Common Stock at the time the incentive stock option is granted.
This provision shall control notwithstanding any contrary terms contained in an
option agreement or any other document.

          6.2  Attribution Rule.   For purposes of subsection 6.1, in
               ----------------                                      
determining stock ownership, an employee shall be deemed to own the stock owned,
directly or 

                                       8
<PAGE>
 
indirectly, by or for his or her brothers, sisters, spouse, ancestors and lineal
descendants. Stock owned, directly or indirectly, by or for a corporation,
partnership, estate or trust shall be deemed to be owned proportionately by or
for its shareholders, partners or beneficiaries. If an employee or a person
related to the employee owns an unexercised option or warrant to purchase stock
of the Company, the stock subject to that portion of the option or warrant which
is unexercised shall not be counted in determining stock ownership. For purposes
of this Section 6, stock owned by an employee shall include all stock actually
issued and outstanding immediately before the grant of the incentive stock
option to the employee.


     SECTION 7.   Adjustments Upon Changes in Capitalization.   The aggregate
                  ------------------------------------------                 
number and class of shares for which options may be granted under this Plan, the
number and class of shares covered by each outstanding option and the exercise
price per share thereof (but not the total price), and each such option, shall
all be proportionately adjusted for any increase or decrease in the number of
issued shares of Common Stock of the Company resulting from a split-up or
consolidation of shares or any like capital adjustment, or the payment of any
stock dividend.

          7.1  Effect of Liquidation, Reorganization or Change in Control.
               ---------------------------------------------------------- 

               7.1.1 Cash, Stock or Other Property for Stock. Except as provided
                     ---------------------------------------
in subsection 7.1.2, upon a merger (other than a merger of the Company in which
the holders of Common Stock immediately prior to the merger have the same
proportionate ownership of Common Stock in the surviving corporation immediately
after the merger), consolidation, acquisition of property or stock, separation,
reorganization (other than a mere reincorporation or the creation of a holding
company) or liquidation of the Company, as a result of which the shareholders of
the Company receive cash, stock or other property in exchange for or in
connection with their shares of Common Stock, any option granted hereunder shall
terminate, but the Optionee shall have the right immediately prior to any such
merger, consolidation, acquisition of property or stock, separation,
reorganization or liquidation to exercise such Optionee's option to the extent
the vesting requirements set forth in the option agreement have been satisfied.

               7.1.2 Conversion of Options on Stock for Stock Exchange.   If the
                     -------------------------------------------------          
shareholders of the Company receive capital stock of another corporation
("Exchange Stock") in exchange for their shares of Common Stock in any
transaction involving a merger (other than a merger of the Company in which the
holders of Common Stock immediately prior to the merger have the same
proportionate ownership of Common Stock in the surviving corporation immediately
after the merger), consolidation, acquisition of property or stock, separation
or reorganization (other than a mere reincorporation or the creation of a
holding company), all options granted hereunder shall be converted into options
to purchase shares of Exchange Stock unless the Company and the corporation
issuing the Exchange Stock, in their sole discretion, determine that any or all
such options granted hereunder shall not be converted into options to purchase
shares

                                       9
<PAGE>
 
of Exchange Stock but instead shall terminate in accordance with the provisions
of subsection 7.1.1. The amount and price of converted options shall be
determined by adjusting the amount and price of the options granted hereunder in
the same proportion as used for determining the number of shares of Exchange
Stock the holders of the Common Stock receive in such merger, consolidation,
acquisition of property or stock, separation or reorganization. Unless
accelerated by the Board, the vesting schedule set forth in the option agreement
shall continue to apply to the options granted for the Exchange Stock.

          7.1.3   Change in Control. In the event of a "Change in Control" as
                  -----------------                                          
defined below, of the Company after the Company has registered any of its equity
securities pursuant to Section 12(b) or 12(g) of the Exchange Act, unless
otherwise determined by the Board prior to the occurrence of such Change in
Control, the following acceleration and cash-out provisions shall apply:

          (a)  Any options or portions thereof outstanding as of the date such
Change in Control is determined to have occurred that are not yet fully vested
on such date shall become immediately exercisable in full, and

          (b)  Optionees shall have, as an alternative to the right to exercise
any nonqualified stock option, the right to elect within 90 days following a
Change in Control to receive in cash an amount equal to the difference between
the option exercise price and the fair market value of the stock on the date of
exercising this election, times the number of shares subject to the option or
portion thereof for which this election is made; provided, however. if during
the six months prior to the date of such Change in Control such Optionee is
subject to Section 16(b) of the Exchange Act with respect to the Company's
securities, then with respect to options held by the Optionee, the period
following the Change in Control during which an election may be made shall be
extended for one month after the end of the six-month period required to avoid
any liability under Section 16(b) of the Exchange Act. The election shall be
made by delivering written notice of making such election to the Company within
the ninety (90) day period. The notice shall specify the options or portions
thereof to which the election relates. The cash-out proceeds shall be paid to
the Optionee or, in the event of death of an Optionee prior to full payment, to
the estate of the Optionee or to a person who acquired the right to exercise the
option by bequest or inheritance.

          7.1.4  Definition of "Change in Control."   For purposes of the Plan,
                 ----------------------------------                            
a "Change in Control" shall mean (a) the first approval by the Board or by the
shareholders of the Company of an Extraordinary Event, (b) a Purchase, or (c) a
Board Change. For purposes of the Plan, an "Extraordinary Event" shall mean any
of the following actions:

               (i)  any consolidation or merger of the Company in which the
     Company is not the continuing or surviving corporation or pursuant to which
     shares of Common Stock would be converted into cash, securities or other
     property other than a merger of the Company in which the holders of Common

                                      10
<PAGE>
 
     Stock immediately prior to the merger have the same proportionate ownership
     of common stock of the surviving corporation immediately after the merger;

               (ii)  any sale, lease, exchange or other transfer (in one
     transaction or a series of related transactions) of all, or substantially
     all, the assets of the Company; or

               (iii)  the adoption of any plan or proposal for liquidation or
     dissolution of the Company.



     For purposes of the Plan, a "Purchase" shall mean the acquisition by any
person (as such term is defined in Section 13(d) of the Exchange Act) of any
shares of Common Stock (or securities convertible into Common Stock) without the
prior approval of a majority of the Continuing Directors (as defined below) of
the Company, if after making such acquisition such person is the beneficial
owner (as such term is defined in Rule 13d-3 under the Exchange Act) directly or
indirectly of securities of the Company representing 20% or more of the combined
voting power of the Company's then outstanding securities (calculated as
provided in paragraph (d) of such Rule 13d-3). For purposes of the Plan, a
"Board Change" shall have occurred if individuals who constitute the Board of
the Company at the time of adoption of this Plan (the "Continuing Directors")
cease for any reason to constitute at least a majority of the Board, provided
that any person becoming a Director subsequent to the date of adoption of this
Plan whose nomination for election was approved by a vote of at least a majority
of the Continuing Directors (other than a nomination of an individual those
initial assumption of office is in connection with an actual threatened election
contest relating to the election of the Directors of the Company, as such terms
are used in Rule 14a-11 of Regulation 14A under the Exchange Act) shall be
deemed to be a Continuing Director.

          7.2   Fractional Shares.  In the event of any adjustment in the number
                -----------------                                               
of shares covered by any option, any fractional shares resulting from such
adjustment shall be disregarded and each such option shall cover only the number
of full shares resulting from such adjustment.

          7.3   Determination of Board to Be Final.  All Section 7 adjustments
                ----------------------------------                            
shall be made by the Board, and its determination as to what adjustments shall
be made, and the extent thereof, shall be final, binding and conclusive. Unless
an Optionee agrees otherwise, any change or adjustment to an incentive stock
option shall be made in such a manner so as not to constitute a "modification"
as defined in Code Section 425(h) and so as not to cause his or her incentive
stock option issued hereunder to fail to continue to qualify as an incentive
stock option as defined in Code Section 422A(b).

     SECTION 8.   Securities Regulation.   Shares shall not be issued with
                  ---------------------                                   
respect to an option granted under this Plan unless the exercise of such option
and the issuance and delivery of such shares pursuant thereto shall comply with
all relevant provisions of law, including, without limitation, any applicable
state securities laws, the Securities Act of 

                                      11
<PAGE>
 
l933, as amended, the Exchange Act, the rules and regulations promulgated
thereunder, and the requirements of any stock exchange upon which the shares may
then be listed, and shall be further subject to the approval of counsel for the
Company with respect to such compliance, including the availability of an
exemption from registration for the issuance and sale of any shares hereunder.
Inability of the Company to obtain from any regulatory body having jurisdiction,
the authority deemed by the Company's counsel to be necessary for the lawful
issuance and sale of any shares hereunder or the unavailability of an exemption
from registration for the issuance and sale of any shares hereunder shall
relieve the Company of any liability in respect of the nonissuance or sale of
such shares as to which such requisite authority shall not have been obtained.

     As a condition to the exercise of an option, the Company may require the
Optionee to represent and warrant at the time of any such exercise that the
shares are being purchased only for investment and without any present intention
to sell or distribute such shares if, in the opinion of counsel for the Company,
such a representation is required by any relevant provision of the
aforementioned laws. At the option of the Company, a stop-transfer order against
any shares of stock may be placed on the official stock books and records of the
Company, and a legend indicating that the stock may not be pledged, sold or
otherwise transferred unless an opinion of counsel is provided (concurred in by
counsel for the Company) stating that such transfer is not in violation of any
applicable law or regulation, may be stamped on stock certificates in order to
assure exemption from registration.

The Plan Administrator may also require such other action or agreement by the
Optionees as may from time to time be necessary to comply with the federal and
state securities laws. THIS PROVISION SHALL NOT OBLIGATE THE COMPANY TO
UNDERTAKE REGISTRATION OF THE OPTIONS OR STOCK HEREUNDER.

     Should any of the Company's capital stock of the same class as the stock
subject to options granted hereunder be listed on a national securities
exchange, all stock issued hereunder if not previously listed on such exchange
shall be authorized by that exchange for listing thereon prior to the issuance
thereof.

     SECTION 9.    Amendment and Termination.
                   ------------------------- 

          9.1  Board Action. The Board may at any time suspend, amend or
               ------------                                             
terminate this Plan, provided that except as set forth in Section 7, the
approval of the holders of a majority of the Company's outstanding shares of
voting capital stock is necessary within 12 months before or after the adoption
by the Board of any amendment which will:

               (a)  increase the number of shares which are to be reserved for
the issuance of options under this Plan;

                                      12
<PAGE>
 
               (b) permit the granting of stock options to a class of persons
other than those presently permitted to receive stock options under this Plan;
or

               (c) require shareholder approval under applicable law, including
Section 16(b) of the Exchange Act.


          9.2   Automatic Termination.   Unless sooner terminated by the Board,
                ---------------------                                          
this Plan shall terminate ten years from the earlier of (a) the date on which
this Plan is adopted by the Board or (b) the date on which this Plan is approved
by the shareholders of the Company. No option may be granted after such
termination or during any suspension of this Plan. The amendment or termination
of this Plan shall not, without the consent of the option holder, alter or
impair any rights or obligations under any option theretofore granted under this
Plan.

     SECTION 10.  Effectiveness of This Plan.   This Plan shall become effective
                  --------------------------                                    
upon adoption by the Board so long as it is approved by the holders of a
majority of the Company's outstanding shares of voting capital stock at any time
within 12 months before or after the adoption of this Plan.

Original Plan adopted by the Board on November 26, 1990 and approved by the
shareholders on November 26, 1990.

                                      13