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.
Released in April of 1987 PC DOS 3.3 which added
support for IBM PS/2 and 1.44 MB 3.5-inch floppy
disk drives. Another major addition was codepage
support for international character sets.
PC DOS 3.3 followed by PC DOS 4.0 in July 1988.