Microsoft open-sources "the earliest DOS source code discovered to date"

15 hours ago

Microsoft released the earliest DOS source code to date, predating MS-DOS branding, including the 86-DOS 1.00 kernel, PC-DOS 1.00 kernel snapshots, and utilities like CHKDSK.
The history involves programmer Tim Paterson creating 86-DOS (originally QDOS) for an Intel 8086-based computer kit, which Microsoft licensed and later bought for the IBM PC 5150.
Microsoft licensed the OS to IBM as PC-DOS while retaining sales rights to other companies, leading to MS-DOS becoming dominant with the rise of IBM PC clones.

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