MS-DOS 5

MS-DOS 5 is a family of versions of MS-DOS, initially released in June 1991.

MS-DOS 5.00
MS-DOS 5.00 was released in June 1991. Various bugs from version 4.01 have been fixed. It added additional utilities for working with memory and disks. A full screen text editor  has replaced the former line editor   supplied since the early days of DOS. The  installation program has been replaced with a new setup that further streamlined the installation procedure.

MS-DOS 5.00a
MS-DOS 5.00a was released in November 1991 and fixed bugs in the initial release, mainly pertaining to FORMAT and FDISK commands.

MS-DOS 5.00A
MS-DOS 5.00A (note the capital letter A) was only released for the Japanese NEC PC-98x1 series computers.

MS-DOS 5.00A-H
MS-DOS 5.00A-H was only released for the Japanese NEC PC-98x1 series computers. It was pre-installed on/bundled with the original PC-9821 computers, and never had a retail release. Some PC-98 games require this specific version of MS-DOS; most notably Policenauts, which is known as being hard to install (for non-Japanese speakers) for this reason.