IBM PC DOS is a DOS system for the IBM Personal
Computer and compatibles, manufactured and sold
by IBM from the 1980s to the 2000s.
PC DOS 5.0 was released in May 1991. The major
new features of the release was ability to run
DOS in HMA and addition of the 122-key keyboard
support. PC DOS 5.0 required at least 256 kB RAM.
In June 1993 IBM released new verion of its
operation system - PC DOS 6.0, which was
introduced as PC DOS 6.1.