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.
DOS 3.10 adds support for networking, used by IBM PC Net and Microsoft Networking products.
Note: Zenith "Z-100" is a non IBM PC compatible, while "Z-100 PC" is a completely different PC compatible machine.