There is a little OS/2 mention there:
"Later that decade, as the PC industry began to take shape, IBM
recognized the importance of controlling the operating system. It
developed OS/2, the next-generation operating system with Microsoft. At
the same time, Microsoft was developing a rival operating system called
Windows. The partnership fractured in 1990 and Microsoft's Windows went
on to dominate the PC operating system business. Those early IBM
decisions--particularly opting for a third-party operating system and
ultimately choosing Microsoft's PC-DOS rather than DRI's
CP/M--ultimately played a huge role in shaping the computer industry
today."
http://news.cnet.com/8301-1001_3-20090728-92/how-ibms-5150-pc-shaped-the-computer-industry/