PC DOS 4.0

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 4.0 added DOS Shell & support for hard disks drives grater then 32 MB. PC DOS 4.0 had many bugs and less free conventional memory than previous PC DOS 3.3. Generally, PC DOS 4.0 regarded as an unpopular release and was replaced by a never version PC DOS 5.0 in May 1991.