Computer firms can sag, too

The year 1982 will be remembered for puncturing the belief that the computer industry had become recession-proof, says Datamation magazine. Although few companies actually failed, as happened during the last bad slump during the early '70s, profits and sales dropped against a background of massive layoffs, cutbacks in the workweek, forced ''vacations,'' and plant closings.

Because computers have become smaller, cheaper, and more widely used, they are now subject to more short-term purchasing decisions, and have become postponable like other equipment.

IBM is now thought to be in one of its strongest positions compared with other makers of both large and small computers. As for the rest of the industry , the magazine predicts the outlook for 1983 will be brightest in the areas of small computers and office systems.