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Microsoft Unveils Earliest DOS Source Code

April 30, 2026 at 14:20
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✦ AI Summary
  • Microsoft has released the oldest known DOS source code
  • This release includes the 86-DOS 1.00 kernel and utilities
  • The announcement highlights DOS's foundational role in computing

This week, Microsoft has made a significant move by releasing what it claims to be "the earliest DOS source code discovered to date." This source code, predating the MS-DOS branding, includes the 86-DOS 1.00 kernel along with development snapshots of PC-DOS 1.00 and essential utilities like CHKDSK.

To provide context, 86-DOS was developed by Tim Paterson for the Intel 8086-based computer kit. Microsoft, needing an operating system for the IBM PC 5150, licensed and eventually acquired 86-DOS, leading to the widespread adoption of MS-DOS across various IBM PC clones in the 1980s and 90s. This historic release acknowledges the operating system's pivotal role in the tech landscape.

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