Business Notes COMPUTERS DEC's

Digital Equipment Corp. used to be the computer industry's most invincible number cruncher. For nearly three decades, the Massachusetts-based manufacturer enjoyed uninterrupted growth as its potent line of VAX midrange computers muscled sales away from IBM by offering comparable computing power at cut-rate prices. But DEC has proved to be vulnerable after all. Caught in an industry-wide slowdown, the company will pare its work force by 9,000, or about 7%, by year's end. Last week DEC posted a quarterly loss of $257 million, the first red ink in its 32-year history and a stunning blow for founder and chairman Kenneth Olsen. Ironically, DEC is now threatened by a shift to less expensive but powerful desktop computers. While DEC's size (1989 sales: $12.9 billion) gives it the resources to develop new products, the company will have to move fast to keep up with the market's changing needs.