SC TO-I/A

QuickLinks -- Click here to rapidly navigate through this document

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE TO
(Rule 13e-4)

TENDER OFFER STATEMENT UNDER SECTION 14(d)(1) or 13(e)(1)
OF THE SECURITIES EXCHANGE ACT OF 1934
(Amendment No. 2)

COMPUTER SCIENCES CORPORATION
(Name of Subject Company (Issuer) and Filing Person (Offeror))

Options to Purchase Common Stock, $1.00 Par Value Per Share,
Having an Exercise Price Per Share of $70.00 or More
(Title of Class of Securities)

42222H106
(CUSIP Number of Class of Securities)
(Underlying Common Stock)

Hayward D. Fisk
Vice President, General Counsel and Secretary
Computer Sciences Corporation
2100 East Grand Avenue
El Segundo, California 90245
(310) 615-0311
(Name, address and telephone number of person authorized to receive notices and
communications on behalf of filing person)

Copy to:

Ronald S. Beard, Esq.
Gibson, Dunn & Crutcher LLP
4 Park Plaza
Irvine, California 92614
(949) 451-3800

CALCULATION OF FILING FEE

Transaction Valuation*	Amount of Filing Fee
$21,898,967	$4,379.79

* Calculated solely for purposes of determining the filing fee. This amount assumes that options to purchase 2,435,440 shares of common stock of Computer Sciences Corporation having an aggregate value of $21,898,967 as of October 23, 2001, will be exchanged pursuant to this offer. The aggregate value of such options was calculated based on the Black-Scholes option pricing model. The amount of the filing fee, calculated in accordance with Rule 0-11 of the Securities Exchange Act of 1934, as amended, equals 1/50th of one percent of the value of the transaction.

/x/ Check box if any part of the fee is offset as provided by Rule 0-11(a)(2) and identify the filing with which the offsetting fee was previously paid. Identify the previous filing by registration statement number, or the Form or Schedule and the date of its filing.

Amount Previously Paid: $4,379.79	Filing Party: Computer Sciences Corporation
Form or Registration No.: Schedule TO (File No. 5-06907)	Date Filed: October 29, 2001

[ ] Check the box if the filing relates solely to preliminary communications made before the commencement of a tender offer.

Check the appropriate boxes below to designate any transactions to which the statement relates:

[ ] third party tender offer subject to Rule 14d-1.

[X] issuer tender offer subject to Rule 13e-4.

[ ] going-private transaction subject to Rule 13e-3.

[ ] amendment to Schedule 13D under Rule 13d-2.

Check the following box if the filing is a final amendment reporting the results of the tender offer. [ ]

    Computer Sciences Corporation ("CSC") hereby amends and supplements its Tender Offer Statement on Schedule TO originally filed on October 29, 2001, and subsequently amended on November 2, 2001 (the "Schedule TO"), with respect to CSC's offer to exchange outstanding options to purchase shares of its common stock, par value $1.00 per share, having an exercise price per share of $70.00 or more for new options to purchase shares of its common stock upon the terms and subject to the conditions described in the offer to exchange dated October 29, 2001.

Item 11. Additional Information

    Item 11 of the Schedule TO is hereby amended and supplemented to include the following information:

    (i) On November 19, 2001, Frederick E. Vollrath, CSC's Corporate Vice President of Human Resources, sent the e-mail filed as Exhibit (a)(13) to all eligible option holders, which is incorporated herein by reference; and (ii) On November 20, 2001, CSC's Stock Options Administration sent the e-mail filed as Exhibit (a)(14) to all eligible option holders who have not yet returned their election form, which is incorporated herein by reference.

Item 12. Exhibits

    Item 12 of the Schedule TO is hereby amended and supplemented to include the following exhibits:

(a)	(13)	E-mail Communication From Frederick E. Vollrath, Corporate Vice President of Human Resources of Computer Sciences Corporation, to All Eligible Option Holders, dated November 19, 2001.
(a)	(14)	E-mail Communication From Computer Sciences Corporation's Stock Options Administration to All Eligible Option Holders Who Have Not Yet Returned Their Election Form, dated November 20, 2001.

1

SIGNATURE

    After due inquiry and to the best of my knowledge and belief, I certify that the information set forth in this Amendment No. 2 to the Schedule TO is true, complete and correct.

COMPUTER SCIENCES CORPORATION

/S/ HAYWARD D. FISK Hayward D. Fisk
Vice President, General Counsel and Secretary

Date: November 20, 2001.

2

INDEX TO EXHIBITS

Exhibit Number	Description
(a)(1)	Offer to Exchange, dated October 29, 2001.*
(a)(2)	Form of Election Form.*
(a)(3)	Form of Cover Letter to Eligible Option Holders.*
(a)(4)	Form of Change in Election Form.*
(a)(5)	Form of Supplementary Australian Offer Document.*
(a)(6)	Form of Letter to Eligible Australian Option Holders.*
(a)(7)	Notice of Change in Contact Telephone Number.*
(a)(8)	E-mail Communication From Van B. Honeycutt, Chairman and Chief Executive Officer of Computer Sciences Corporation, to All Eligible Option Holders, dated October 29, 2001.*
(a)(9)	Press Release Issued by Computer Sciences Corporation, dated October 29, 2001.*
(a)(10)	E-mail Communication From Frederick E. Vollrath, Corporate Vice President of Human Resources of Computer Sciences Corporation, to Certain Senior Human Resource Executives, dated October 29, 2001.*
(a)(11)	E-mail Communication From Leon J. Level, Chief Financial Officer of Computer Sciences Corporation, to Certain Senior Finance Executives, dated October 29, 2001.*
(a)(12)	E-mail Communication From Frederick E. Vollrath, Corporate Vice President of Human Resources of Computer Sciences Corporation, to All Eligible Option Holders, dated November 1, 2001.*
(a)(13)	E-mail Communication From Frederick E. Vollrath, Corporate Vice President of Human Resources of Computer Sciences Corporation, to All Eligible Option Holders, dated November 19, 2001.
(a)(14)	E-mail Communication From Computer Sciences Corporation's Stock Options Administration to All Eligible Option Holders Who Have Not Yet Returned Their Election Form, dated November 20, 2001.
(d)(1)	Computer Sciences Corporation's 1990 Stock Incentive Plan, filed as Exhibit 4(a) to the Company's Registration Statement on Form S-8 filed on August 15 1990, and incorporated herein by reference.
(d)(2)	Computer Sciences Corporation's 1992 Stock Incentive Plan, filed as Exhibit 10.8 to the Company's Quarterly Report for the Quarterly Period ended June 28, 1996, and incorporated herein by reference.
(d)(3)	Computer Sciences Corporation's 1995 Stock Incentive Plan, filed as Exhibit 10.16 to the Company's Quarterly Report for the Quarterly Period ended September 29, 1995, and incorporated herein by reference.
(d)(4)	Computer Sciences Corporation's 1998 Stock Incentive Plan, filed as Exhibit 10.10 to the Company's Quarterly Report for the Quarterly Period ended July 3, 1998, and incorporated herein by reference.
(d)(5)	Form of Stock Option Agreement.*
(d)(6)	Form of Stock Option Schedule.*

*

Previously filed as an exhibit to the Schedule TO or an amendment thereto.

QuickLinks

SCHEDULE TO (Rule 13e-4)
CALCULATION OF FILING FEE
Item 11. Additional Information
Item 12. Exhibits
SIGNATURE
INDEX TO EXHIBITS

EX-99.(A)(13)

QuickLinks -- Click here to rapidly navigate through this document

Exhibit (a)(13)

[TEXT OF E-MAIL SENT BY CORPORATE VP OF HUMAN RESOURCES, ON NOVEMBER 19, 2001, TO ALL ELIGIBLE OPTION HOLDERS]

We have had a very good response to the Stock Option Exchange Offer so far - approximately 60% of the eligible optionees have completed and returned their Election Forms. Acknowledgments of receipt are being e-mailed twice a week. If you do not receive one within that time frame, please contact us.

If you have not yet returned your Election Form (preferably by fax to 310.414.5858), please remember that the deadline for our receipt of Election Forms is 5:00 p.m., Pacific time, on Wednesday, November 28, 2001.

A number of you have used the dedicated CSC e-mail box (options@csc.com) to ask questions regarding the Exchange Offer. Two of these questions are of sufficiently broad application that we thought it would be useful to share the answers with all of you.

WHAT HAPPENS IF CSC IS ACQUIRED AFTER MY OLD OPTIONS ARE CANCELED, BUT BEFORE MY NEW OPTIONS ARE ISSUED?

While we currently have no plans to enter into any such transaction, it is possible that CSC could be acquired during this period of time. In that event, you would not be issued any new options or other consideration unless the acquiring entity, in its sole discretion, agreed to the issuance. Although we, consistent with our fiduciary duties to our stockholders, might attempt to negotiate such an agreement with the acquiring entity, there can be no assurance that any such attempt would be successful.

WHAT HAPPENS IF I GO OUT ON LEAVE AFTER MY OLD OPTIONS ARE CANCELED, BUT BEFORE MY NEW OPTIONS ARE ISSUED?

In order to receive the new options, you must be a regular, full-time employee of CSC or its subsidiaries on the date they are issued. In addition, during the entire period between the old option cancellation date and the new option issuance date, you must either be a regular, full-time employee, or be on a leave of absence that has been specifically designated as an "approved," leave for purposes of stock options by Van Honeycutt, Chairman and Chief Executive Officer, or by me. Certain types of leaves, such as military leaves and leaves taken by U.S. employees pursuant to the Family Medical Leave Act, have been so designated as "approved." Please contact me if you have any questions regarding an impending leave of absence.

If you have any other questions, please contact us by telephone (310.414.4600) or e-mail (options@csc.com).

QuickLinks

Exhibit (a)(13)

EX-99.(A)(14)

QuickLinks -- Click here to rapidly navigate through this document

Exhibit (a)(14)

[TEXT OF E-MAIL SENT BY STOCK OPTIONS ADMINISTRATION, ON NOVEMBER 20, 2001, TO ALL ELIGIBLE OPTION HOLDERS WHO HAVE NOT YET RETURNED THEIR ELECTION FORMS]

Subject: DEADLINE Approaching - Election Form Not Yet Received from - [optionee name]

As of 10:00am PST today, we have not received your completed Election Form for the Stock Option Exchange Offer. Be aware that the deadline to respond is 5:00pm PST on Wednesday, November 28, 2001. There is absolutely no flexibility to the deadline.

If you already sent it in, there may have been faxing and/or postal service problems, so you will need to send it again. We strongly recommend you fax another copy to 310-414-5858.

And if you never received the offer package in the first place, please reply to this e-mail immediately so we can send you the complete package via e-mail.

DON'T wait to the last minute and risk the fax line being busy.

DO be sure to mark the Election box of your choice (Accept or Reject) and sign the form.

DO respond regardless of your choice, to avoid continuing reminder notices.

E-mail acknowledgements for Election Forms received will increase in frequency from twice weekly to daily as of Monday, November 26.

Thank you and regards,
Lisa Desemone
Director, Benefits Accounting

QuickLinks

Exhibit (a)(14)