Firms Plan Standard Unix System for PCs

Three software companies announced plans to develop a standard version of the Unix operating system for IBM and IBM-compatible personal computers.

Santa Cruz Operation Inc. said it will work with American Telephone & Telegraph Co. and Intel Corp. on the software project that would give PC users an alternative to the traditional MS-DOS and OS/2 computer operating systems used in personal computers made by International Business Machines Corp., Compaq Computer Corp. and others.

Analysts see the agreement as a potential blow to Redmond, Wash.-based Microsoft, which sells the MS-DOS and OS/2 operating systems for IBM and compatible personal computers.