Barely 12 years ago MS-DOS 1.0 was introduced as the operating system for the IBM PC by William H. Gates, the then modestly heeled cofounder of Microsoft. By the time the latest version -- MS-DOS 6.0 -- came out, last month, Gates's personal net worth had passed $6 billion. Each successive version has significantly enhanced the functionality of IBM-compatible PCs at a reasonable cost. Here are some of 6.0's advances:

Data compression. Effectively doubles hard-disk storage. All saved data are automatically compressed when stored and uncompressed when retrieved.

Memory management. Improved program resolves "out of memory" situations previously caused by misapportioned expanded and extended memory.

Simplified backup. Safeguards data by storing user-designated files on floppies or on a network.

Virus protection. Detects and removes known viruses. Has an update capability.

File transfer. Easily copies files via cable between a desktop and a portable.

MS-DOS 6.0 is from Microsoft, in Redmond, Wash. An upgrade is $49.95 through June 1993; $129.95 thereafter.

-- Robert A. Mamis