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.
Microsoft intentionally skipped "6.1" to prevent confusion with IBM's independently produced PC-DOS 6.1. Microsoft also made a free/inexpensive 6.0 -> 6.2 step up kit available.
This update corrects some major bugs in DoubleSpace, introduces ScanDisk, adds automounting of compressed floppies, and a tool to uncompress DoubleSpace compressed drives.
The non-upgrade versions can be installed on a blank drive or overwrite any existing DOS.
The regular upgrade versions can only be installed if a previous qualifying DOS is present, and provides an uninstall option.
The 6.2 Step-Up will only upgrade from MS-DOS 6.0.