Originally 86-DOS, written by Tim Paterson of Seattle Computer Products, DOS was a rough clone of CP/M for 8086 based hardware. Microsoft purchased it and licensed it to IBM for use with Microsoft's IBM PC language products. In 1982, Microsoft began licensing DOS to other OEMs that ported it to their custom x86 hardware and IBM PC clones.
For IBM-specific releases, please see the IBM PC-DOS product page.
MS-DOS 6.0 includes many new utilities and features, including a disk defragmenter, disk compression, anti-virus, a new backup system, and pc-pc file transfer tools. It was heavily criticized as buggy by the media, primarily due to file corruption issues with DoubleSpace and the lack of tools to repair such issues.
Note that the boot sector OEM ID of "MSDOS6.0" is correct and genuine. Microsoft reverted to using "MSDOS5.0" on later disks.
The "Full" version can be installed on a blank drive or as an upgrade with an uninstall option.
The non-upgrade versions can be installed on a blank drive or overwrite any existing DOS.
The Upgrade versions can only be installed if a previous qualifying DOS is present, and provides an uninstall option.