First IBM brought out a new line of personal computers called PS/2, and soon after Microsoft and IBM brought out a new software operating system called OS/2. The computing public understandably associates the two, which is undoubtedly what IBM had in mind.

But you don't need a PS/2 to run OS/2. Not all the systems in the PS/2 line will run it, and at the moment there's good reason to question whether you need OS/2 at all.

The new operating system is designed to make full use of the Intel 80286 microprocessor. It is the successor to the Intel 8088 and 8086, which were the brains behind the first generation of IBM personal computers and their many clones. The 80286 is the brain behind the IBM AT and its clones, as well as the PS/2 models 50 and 60.

The 80286 will run software written for the older chips, and it will do so faster. But without the new operating software, that's about all the 80286 can do. The 80286 microprocessor is designed to access up to 16 megabytes of memory and has enough muscle to power more than one program at a time. The older operating software, PC-DOS and MS-DOS, don't have this capability.

So enter the long-awaited OS/2, which has been much heralded by the computer trade press.

But if you have a standard PC, XT or compatible, you can't run it. At the moment that hardly matters because the operating system itself is all that is available. There is no application software written for OS/2. And when the first wave of applications comes in, it is likely to be nothing more than existing programs rewritten to run with OS/2. So you'll still be in good shape with your present PCs and XTs.

And remember: There are millions of PCs, XTs and compatible systems out there -- some estimates run as high as 12 million. The number of 80286 machines is far fewer, although they have finally begun to outsell PCs and XTs. Software developers cannot ignore such a large base of computers to go after a far smaller number of systems using a new and untried operating system.

This means there will be lots of new software for old machines running PC-DOS and MS-DOS for years to come. If you doubt that, look at the Apple computers, where software for the Apple II line continues to be produced despite the availability of much more powerful Apple systems.

Even Microsoft, despite its heavy investment in OS/2, still is competing vigorously in the DOS world, as shown by the development and heavy promotion of Microsoft Works.

With a $199 list price, the software is a relatively inexpensive and smoothly integrated package that includes a word processor, spreadsheet, data base and communications program.

MS-Works is designed to operate either with a mouse or through keyboard commands. Its use of pull-down menus is similar to that of software written for the Apple Macintosh, which has been acclaimed for its ease of use.

This is worth mentioning because one of the promised benefits of OS/2 is a new and friendlier "user interface" similar to Macintosh's. It appears, however, that some of this ease of use already is being included in software written for the old operating system, another reason to question the need for OS/2.

And something else has happened to make you think twice about OS/2. Intel has introduced the 80386 chip, which is more powerful than the 80286 and by all accounts, much better engineered. The market now is flooded with 80386 computers, which cost more than their 80286 counterparts, but less than an IBM AT did just two years ago.

The reason it took nearly four years for OS/2 to arrive is that the 80286 had flaws that made the operating software difficult to develop. The 80386 is better and, while it will run OS/2, Microsoft is said to have ready an operating system designed specifically for it.

But you won't see it anytime soon because the company needs to recoup its development costs for OS/2 before it brings out what would undoubtedly be a stiff competitor to its own product.

If Microsoft brought out an operating system for the 80386, it would likely be the end of OS/2 because software developers would rush to write programs to run under the better and more powerful 80386. We would never see much, if any, application software for OS/2.

It's possible, of course, that someone will bring out a new must-have program that will run only under OS/2 and it will do for the new operating system what Lotus 1-2-3 did for the IBM PC and DOS.

But until that happens, you would be wise to view OS/2 as a scheme to separate you from your present computer and a lot of money. There will be plenty of time to upgrade when the software demands that you do so and by then, prices of 80286 machines will have dropped ever more than they have already.

Brit Hume is a contributor to the Washington Post Writers Group. Hume is an ABC News Capitol Hill correspondent and the founding editor of a computer newsletter.