Programming Windows: Microsoft OS/2 (Premium)

While the IBM PC and its follow-up, the hard drive-based PC XT, were huge successes, the firm stumbled with subsequent models. The IBM PCjr, an ill-fated attempt to capitalize on the home market, was an outright disaster. And the IBM AT, IBM’s first non-8088-based PC, shipped in 1984 with an Intel 80286, a chip that Bill Gates had called “brain-dead.” He had advised IBM to wait for the more powerful and 32-bit 80386, which wouldn’t even be announced until a year later.

Worse, MS-DOS---or, PC-DOS, as IBM called it---had been quickly released to accommodate IBM’s rush schedule for the first PC in 1981 and the limitations imposed by its 16/8-bit Intel 8088 processor and its weird segmented memory model in which only the first 640 KB of system RAM was easily accessible. And just a few years later, DOS was having a hard time keeping up with the changes coming in subsequent 16- and 32-bit Intel chipsets.

So, in June 1985, IBM and Microsoft signed a long-term Joint Development Agreement (JDA) in which the two firms agreed to create a new operating system, based on MS-DOS/PC-DOS, that could better take advantage of the coming wave of 32-bit microprocessors. The move elevated Microsoft from its role of software supplier to being a true partner with IBM, creating an OS duopoly that would span both IBM’s PCs and the many clones that had sprung up in its wake.

“'It’s by far the biggest contract we’ve ever signed,” Gates told The New York Times at the time. The publication also noted that Microsoft was “already working on future versions of its operating systems, known as versions 4.0 and 5.0, that will take advantage of more powerful computers now being built.”

Originally called CP/DOS and then Advanced DOS, this new system was viewed within IBM as a way to link up all of its computing products, from its mainframes to its personal computers. But for Microsoft, the JDA and Advanced DOS simply represented a way to keep its biggest customer happy. And besides, the JDA specified that Microsoft could continue selling Advanced DOS to third-parties, just as it had been doing with MS-DOS. Gates’ master strategy could continue.

The two firms immediately began squabbling over the design of the new OS, partially due to the different corporate cultures and partially because neither was particularly interested in ceding any more control to the other. The big break came when Gates wanted Advanced DOS to target only the 80386 and newer chipsets, but IBM wanted to support the “brain-dead” 286 as well; it wouldn’t abandon its PC AT customers. Worse, IBM never even ordered any 80386 chips when they shipped in 1986, and clone-maker Compaq beat IBM to market with the first PC to feature the new 32-bit design.

There were also arguments over Windows, the graphical operating environment for DOS that Microsoft had first released in 1985. The JDA suggested that Windows and an IBM-made PC-DOS-based windowing environment called ...

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