Apple copyrighted the distinctive ''look and feel'' of the Macintosh graphical user interface and has been quick to sue companies it believes have infringed on it. Apple has suits pending against the Microsoft Corporation of Redmond, Wash., and the Hewlett-Packard Company of Palo Alto, Calif., contending that their software products infringe on the Macintosh copyright. Ideas and Expressions

Apple, based in Cupertino, Calif., said it believed Xerox's complaint was without merit.

''The Xerox complaint seems to confuse the distinction between ideas and expression; copyright protects expression, not ideas,'' said Stacey Byrnes, an Apple spokeswoman. ''Apple intends to prove in court that the audio-visual expressions in the Lisa and Macintosh interfaces were wholly original to Apple and duly registered with the copyright office.''

Xerox contends that Apple ''intentionally and purposefully concealed'' the derivation of the Lisa and Macintosh software from Xerox software. It said that Apple's copyrights on Lisa and Macintosh software were invalid and that the company had unjustly received benefits that rightfully belong to Xerox.

''Xerox is not a litigious company,'' David T. Kearns, Xerox's chairman and chief executive, said in a statement, ''but we have no other recourse than to seek relief from the court for actions we believe to be unlawful and unfair and, if allowed to continue unchallenged, to be against the interest of Xerox, its shareholders and the computer industry.''

He said efforts to reach a settlement with Apple, including a licensing proposal, had been rebuffed. #1979 Visit Recalled But Xerox, based in Stamford, Conn., has begun entering licensing agreements with other companies, including Sun Microsystems Inc. and Metaphor Computer Systems Inc. And it announced in May that it intended to fully protect its licensing rights.