[rxh4n1]

IBM had OS2 Warp. It failed. They still use it internally.

[Will88]

Here is paragraph that explains how IBM's fear of further anti-trust investigations caused them to give up control of the PC operating system in such a way as to allow Microsoft to become what it became.

On Nov. 6, 1980, the contract that would change the future of computing was signed: IBM would pay Microsoft $430,000 for what would be called MS-DOS. But the key provision in that agreement was the one that allowed Microsoft to license the operating system to other computer manufacturers besides IBM — a nonexclusive arrangement that IBM agreed to in part because it was caught up in decades of antitrust investigations and litigation. IBM’s legal caution, however, would prove to be Microsoft’s business windfall, opening the door for the company to become the dominant tech company of the era.

THE AGREEMENT THAT CATAPULTED MICROSOFT OVER IBM