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.
In September of 1981 IBM release an updated
verion of it's PC DOS 1.0. The new version 1.1
added support for 320 kB double-sided floppy
PC DOS 1.1 followed by PC DOS 2.0 in March of