<PAGE>



                               SUMMIT DESIGN, INC.
                              EMPLOYMENT AGREEMENT

EMPLOYEE:             JOHN DIFERDINANDO
EFFECTIVE DATE:       April 15, 1997

This Agreement is entered into as of the above date by and between SUMMIT
DESIGN, INC., a Delaware corporation ("SUMMIT") and the above-named employee
("DiFerdinando").

1.      EMPLOYMENT AND DUTIES. SUMMIT hereby employs DiFerdinando to serve
and perform in the role of Vice President of Worldwide Marketing, SLDA
Products reporting to the Chief Executive Officer or Chief Operating Officer
or General Manager, SLDA Products. DiFerdinando agrees to perform the duties
of this position to the best of his ability and to devote full time and
attention to the transaction of SUMMIT's business.

2.      TERM AND TERMINATION.

        (a) This Agreement shall have an initial term of four (4) years,
commencing on the effective date, unless sooner terminated in accordance with
Subsection 2(b) and/or 2(c) and/or 2(d) and/or 2(e) below. After the initial
term of four (4) years, or any extension thereof, the term of the Agreement
shall automatically extend for additional one (1) year periods unless
terminated by either party with at least ninety (90) days' advanced written
notice prior to the end of the then-current term. Both parties acknowledge
that the employment created herein is Employment-at-Will and may be
terminated with or without cause under the terms stated herein.

        (b) In the event that DiFerdinando notifies Summit of termination of
his employment with Summit for any reason other than specified in Section
2(d), this Agreement shall terminate as of the date of such notification.
Termination under this Section 2(b) is "Resignation".

        (c) In the event that Summit notifies DiFerdinando of termination of
his employment by Summit because DiFerdinando willfully abandoned the duties
of his position or engaged in any business or criminal practice which the
Chief Executive Officer, or Chief Operating Officer, or Board of Directors
reasonably determines is detrimental or harmful to the good name, goodwill,
or reputation of Summit, or which does or could adversely affect the
interests of Summit, then this Agreement shall terminate as of the date of
such notification. Termination under this Section 2(c) is "Cause".

        (d) In the event that DiFerdinando notifies Summit of his resignation
as an employee of Summit because Summit has required (in writing)
DiFerdinando


                                       1

<PAGE>

to perform solely in any role other than Vice President of Worldwide
Marketing, SLDA Products without DiFerdinando's consent (in writing), then
this Agreement shall terminate as of the date of such notification.
Termination under this Section 2(d) is "Construction".

        (e) In the event that Summit notifies DiFerdinando of termination of
his employment by Summit for any reason other than specified in Section 2(b)
and/or 2(c) and/or 2(d), this Agreement shall terminate as of the date of
such notification. Termination under this Section 2(e) is "convenience".

        (f) Notwithstanding the above, termination of this Agreement shall
not release DiFerdinando from any obligations under Sections 4, 5, and 6
hereof.

3.      COMPENSATION AND BENEFITS. In consideration of the services to be
performed by DiFerdinando, and effective July 1, 1997, SUMMIT agrees to pay
DiFerdinando the compensation and extend to DiFerdinando the benefits
consisting of the following:

        (a) Annual Base Salary of $130,000, paid twice monthly and prorated
and beginning on the first pay period following the date agreed upon by
DiFerdinando and the Chief Executive Officer.

        (b) Annual bonus of 25% of base salary, as determined by the terms
and conditions specified in the Executive Bonus Plan.

        (c)    Equity

                      (i) Summit hereby grants DiFerdinando an incentive stock
        option of 25,000 shares of Summit common stock at a price to be
        determined at the close of the market on the day of approval by the
        Summit Design Board of Directors. These shares are governed by the terms
        and conditions of the Summit Incentive Stock Option Plan ("ISO Plan").
        Notwithstanding the terms and conditions of the ISO Plan, 25% of these
        shares shall vest 12 months after the effective date of this Agreement
        and the remaining shares shall vest at a rate of 1/36 per month for the
        next 36 months.

                      (ii) In addition, if more than 50% of the assets or more
        than 50% of the outstanding shares of Summit are sold to another
        company, all of the shares covered under this Section 3(c)(i) shall be
        100% vested at closing of the transaction.

                      (iii) In addition, if this Agreement is terminated for
        Construction as defined in Section 2(d) or convenience as defined in
        Section 2(e), all shares covered under this Section 3(c)(i) shall be
        100% vested.

                      (iv) In addition, if this Agreement is terminated for
        Resignation as defined in Section 2(b) or Cause as defined in Section
        2(c) within 36 months of the effective date of this Agreement, then
        Summit


                                       2

<PAGE>

        shall have the right to repurchase all vested shares and all unvested
        shares for their issued price. For the purpose of this Section
        3(c)(iv), "repurchase" shall mean payment of the issued price for
        return of any shares purchased by DiFerdinando and cancellation of
        all outstanding and unexercised options to purchase shares.

                      (v) In addition, in the event of death or disability,
        vesting shall continue for twelve (12) months.

        (d)     DiFerdinando shall be provided the right to participate in the
health, dental, and life insurance programs provided for the senior level
executives of Summit.

        (e)     DiFerdinando shall be granted fifteen (15) days of paid time
off, in addition to eleven (11) paid holidays and up to seven (7) days paid
in case of illness, during his first year of employment and each year
thereafter. This paid time off shall be available for use according to the
standard policy of Summit.

        (f)     In the event that this Agreement is terminated for
Construction as defined in Section 2(d) or Convenience as defined in Section
2(e), then Summit shall pay DiFerdinando $10,833.00 per month plus all
insurance benefits normally paid by Summit. This payment shall continue
monthly for six (6) months provided, however, that if DiFerdinando accepts
full-time employment from another party prior to the end of such six (6)
months, these monthly payments and benefits shall immediately terminate.

4.      RELOCATION. Summit Design agrees to pay for relocation of
DiFerdinando and his family from Pennsylvania to Oregon, provided that the
move takes place by September 30, 1997, and according to the following terms:

        (a)     Reimbursement for the cost of moving household goods by a
Summit approved moving company, including packing, unpacking, insurance, and
two vehicles in accordance with attached Exhibit A;

        (b)     equity protection in his Pennsylvania home that will net
DiFerdinando proceeds equal to $411,000, available for settlement by July 31,
1997;

        (c)     three (3) annual payments not to exceed $3,720, due upon
settlement and at twelve (12) month intervals thereafter, to compensate
DiFerdinando for the difference in interest cost on his home mortgage;

        (d)     reimbursement of closing costs equal to no more than 1% of
the purchase price of his home in Oregon;

        (e)     reimbursement of the cost to transport DiFerdinando, his
spouse, and children from Pennsylvania to Oregon under the terms of Summit's
Travel Policy;

                                       3

<PAGE>

        (f)     $1,500 per month, plus storage fees, for up to 30 days for
total temporary living expenses in the Portland area, and one (1) rental car
until movers arrive with DiFerdinando's personal auto; and

        (g)     up to two (2) house hunting trips for DiFerdinando and his
spouse to the Portland area, including air, rental car, accommodations, and
meals in accordance with the Summit Design Travel Policy.

5.      CONFIDENTIALITY. DiFerdinando acknowledges that certain customer
lists, design work, and related information, equipment, computer software,
and other proprietary products and information, whether of a technical or
non-technical nature, including but not limited to schematics, drawings,
models, photographs, sketches, blueprints, printouts, and program listings of
SUMMIT, collectively referred to as "Technology", were and will be designated
and developed by SUMMIT at great expense and over lengthy periods of time,
are secret and confidential, are unique and constitute the exclusive property
and trade secrets of SUMMIT, and any use or disclosure of such Technology,
except in accordance with and under the provisions of this or any other
written agreements between the parties, would be wrongful and would cause
irreparable injury to SUMMIT. DiFerdinando hereby agrees that he will not, at
any time, without the express written consent of SUMMIT, publish, disclose,
or divulge to any person, firm, or corporation any of the Technology, nor
will DiFerdinando use, directly or indirectly, for DiFerdinando's own benefit
or the benefit of any other person, firm, or corporation, any of the
Technology, except in accordance with this Agreement or other written
agreements between the parties.

6.      INVENTIONS. All original written material including programs, charts,
schematics, drawings, tables, tapes, listings, and technical documentation
which are prepared partially or solely by DiFerdinando in connection with
employment by SUMMIT shall belong exclusively to SUMMIT.

7.      RETURN OF DOCUMENTS. DiFerdinando acknowledges that all originals and
copies of records, reports, documents, lists, plans, drawings, memoranda,
notes, and other documentation related to the business of SUMMIT or
containing any confidential information of SUMMIT shall be the sole and
exclusive property of SUMMIT, and shall be returned to SUMMIT upon the
termination of employment for any reason whatsoever or upon the written
request of SUMMIT.

8.      COMPLIANCE. DiFerdinando agrees to comply with all of SUMMIT's
written employment policies, guidelines, and procedures as contained in an
employment manual, including revisions and additions thereto.

9.      INJUNCTION. In addition to all other legal rights and remedies,
SUMMIT shall be entitled to obtain from any court of competent jurisdiction
preliminary and permanent injunctive relief of any actual or threatened
violation of any term hereof without requirement of bond, as well as an
equitable accounting of all profits or benefits arising out of such violation.


                                       4

<PAGE>

10.     WAIVER. The waiver of either party of a breach of any provision of
this Agreement shall not operate or be construed as a waiver of any
subsequent breach thereof.

11.     DISPUTES. The legal relations of the parties hereunder, and all other
matters hereunder, shall be governed by the laws of the State of Oregon.
Unresolved disputes shall be resolved in a court of competent jurisdiction in
Washington County, Oregon, and all parties hereto consent to the jurisdiction
of such court.

12.     ENTIRE AGREEMENT. This Employment Agreement sets forth the entire
agreement between the parties hereto, and fully supersedes any and all prior
employment agreements or understandings, written or oral, between the parties
hereto pertaining to the subject matter hereof. No modification of amendment
hereof is effective unless in writing and signed by both parties.

IN WITNESS WHEREOF, the parties have executed this Agreement as of the date
first herein above written.


"EMPLOYER":                  SUMMIT:
                             A Delaware Corporation

                             By:  /s/  LARRY J. GERHARD
                                  ---------------------------------
                                  Larry J. Gerhard
                                  Chief Executive Officer, SUMMIT


"EMPLOYEE":                  By:  /s/  JOHN DIFERDINANDO
                                  ---------------------------------
                                  John DiFerdinando




                                    EXHIBIT A


SHIPMENT OF HOUSEHOLD GOODS
---------------------------

A Summit-approved moving company of your choice will provide this service for
you. The cost should be billed directly to you and will be promptly
reimbursed by Summit.

SERVICES WILL INCLUDE:
-   Unlimited poundage of personal effects, from old principal residence to new
    principal residence, for you and your accompanying family members.


                                       5

<PAGE>

-   Packing and unpacking (you must request the unpacking service when
    receiving quotes from moving companies)
-   Thirty (30) days of storage for your household goods
-   Maximum of two (2) operational vehicles (motorcycle can be substituted)

EXCLUDED ITEMS:
-   Storage of vehicles
-   Extra pick ups/deliveries
-   Weekend pick up/delivery
-   Storage over 30 days
-   Shipment of: Accounts, bills, deeds, letters of credit, jewelry, furs,
    precious stones, bullion and precious metals, watches, stamps (including
    stamp collections), currency, money, notes, securities or evidence of debt,
    ammunition, flammables, foliage, firewood, alcohol, wine and any type of
    liquid in bottles/containers (cooking oil, condiments, medicine,
    pesticides), animals, and aircraft
-   Unique items not considered household goods

INSURANCE

Household goods, with certain exclusions as stated below, are insured for
replacement value up to $250,000.00. Replacement value means that your goods
will be adjusted based on today's cost of the item of "like kind" and
quality. Coverage applies while your goods are in transit and while in
storage. Should the value of your goods exceed $250,000.00, you must contact
Human Resources at 503-526-6374.


                                       6


<PAGE>



                          ADDENDUM TO EMPLOYMENT AGREEMENT


     Pursuant to the Employment Agreement between John DiFerdinando
("Employee") and Summit Design, Inc.("Employer"), dated April 15, 1997, and
as part of the relocation package referenced therein, Employer is to assume
the cost of maintaining Employee's residence in Pennsylvania until it can be
sold.  By mutual agreement of the parties, this Addendum shall supplement and
amend the terms of the Employment agreement to clarify the rights and
obligations of both parties thereto relative to Employee's house in Lansdale,
PA.  The residence is commonly known as 1310 Sunny Ayr Way, Lansdale, PA
19446.

     Section 4 of the Employment Agreement is hereby supplemented and amended
as follows:

     Beginning on July 15, 1997, and continuing thereafter for a period not
to exceed three years or until the house is sold, whichever occurs first,
Employer shall undertake the following obligations with respect to the
Employee's Lansdale house:

     1.   Employer will pay the existing monthly principal and interest
payments on the Lansdale house, pay the insurance, and pay the real property
taxes on the property.  The insurance shall be maintained at its current
amount and Employer shall be named as an additional loss payee on the policy.

     2.   Employer shall be responsible for the ordinary upkeep of the
property.

          a.   Ordinary upkeep shall mean maintaining the existing yard and
landscaping.  Employer shall be responsible for mowing the lawn, weeding the
yard and flower beds, watering the plants, and trimming trees and shrubs.

          b.   Ordinary upkeep shall also mean keeping the house in good
repair. Employer's responsibilities shall include the repair of broken
windows, doors, and pipes.

          c.   Under no circumstances shall the Employer be responsible for
making cosmetic repairs or repairs required by a lender or prospective
purchaser of the property.

     3.   Employer shall also be responsible for maintaining the utilities
for the house including water, electricity, heat, and phone service.
Employer is obligated to continue such utility service only to the extent
that such utilities are necessary to maintain the house and yard or to the
extent that such utilities are necessary to facilitate the sale of the house.

/ / /

/ / /

/ / /


<PAGE>

     4.   There shall be no obligation for Mr. DiFerdinando to repay Summit
Design for the cost of assuming the financial obligations and upkeep of the
Lansdale house.

     Except as specifically amended above, the remaining terms and conditions
of the Employment Agreement remain in effect and are hereby reconfirmed.

     DATED this 15th day of July, 1997


     EMPLOYER:

                         Summit Design, Inc., a Delaware Corporation


                         /s/ Arthur Fletcher
                         --------------------------------------------
               Name:       Arthur Fletcher
               Title:      Treasurer and Director of Financial Planning


     EMPLOYEE:

                         /s/ John DiFerdinando
                         --------------------------------------------
                         John DiFerdinando