INTEGRATED                                                         EXHIBIT 10.13
SYSTEMS
LOGO                         1988 Stock Option Plan
                         Stock Option Exercise Agreement

I hereby  elect to exercise the number of shares of Common  Stock,  as set forth
below:

Optionee:         __________________ Grant Number:          ____________________
Social Security #:__________________ Date of Option Grant:  ____________________
Address: ___________________________ Number of Shares to Exercise: _____________
         ___________________________ Exercise Price per Share: _________________
Type of Option: [ ] Nonqualified Stock Option  Total Exercise Price:____________
                [ ] Incentive Stock Option

The method I choose to exercise these shares is indicated below:

[  ] Cash:  Attached  is  a  check in the  amount of  $_____________  payable to
     Integrated Systems, Inc. for the total exercise price of these shares. If I
     am  exercising  a  nonqualified  option,  a second  check in the  amount of
     $___________ is attached to pay for the taxes due on the day of exercise (I
     understand these taxes will be calculated for me.)

__________     Please instruct the transfer agent to issue the certificate in my
               name and mail it to me at my home address listed above.

__________     Please  instruct the transfer  agent to issue the  certificate in
               street name and mail it directly to the broker listed below:

               _______________________________________ (Broker Name)
 
               _______________________________________ (Company Name)

               _______________________________________ (Street Address)

               _______________________________________ (City, State, Zip Code)

               _______________________________________ (Phone Number)

               _______________________________________ (Fax Number)

               _______________________________________ (Account Number)

[ ]  Same-Day-Sale:  I  choose  to  pay for the  exercise of this option and any
     taxes  due on the day of  exercise  from the  proceeds  of a  same-day-sale
     through Hambrecht & Quist,  Inc. I further  understand that I am guaranteed
     the bid side net price through this broker with no  transaction  or service
     fees.  I have  indicated  below if I wish to sell at  market  price or if I
     choose to specify a selling price (a "good until canceled" order).

         _____  I choose to sell my shares at market price.
         _____  I choose to sell my shares at the specified price of $__________
                per share.

[ ]  Payment  from  Margin  Account:  I choose  to pay for the  exercise of this
     option and any taxes due on the day of exercise  from my margin  account at
     Hambrecht  & Quist,  Inc.  I have  sufficient  funds in my account to cover
     these costs.

     Tax Consequences. Optionee understands that optionee may suffer adverse tax
consequences  as a result of optionee's  purchase or  disposition of the shares.
Optionee  represents  that  optionee has  consulted  with any tax  consultant(s)
optionee deems  advisable in connection  with the purchase or disposition of the
shares and that optionee is not relying on the company for any tax advice.

     Entire Agreement.  The Plan and Grant are incorporated herein by reference.
This Exercise Agreement,  the Plan and the Grant constitute the entire agreement
of the  parties and  supersede  in their  entirety  all prior  undertakings  and
agreements  of the  Company and  Optionee  with  respect to the  subject  matter
hereof, and is governed by California law except for that body of law pertaining
to conflict of laws.

Date:    ________________________             _________________________________
                                                    Signature of Optionee

Approved:       _________________             _________________________________
                                                         Printed Name

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