PDP-10

Digital Equipment Corporation time-sharing mainframe; the machine at Harvard on which Gates, Allen, and Davidoff wrote the original Altair BASIC interpreter in early 1975, per the surviving listing's own header comment ("originally written on the PDP-10 from February 9 to April 9"), before it was ported to run on the Altair 8800 itself.

References

• claim-gates-2025-released-original-1975-altair-basic-source-scan
• Captures: 10-inbox/raw/2026-07-30-does-the-surviving-original-microsoftaltair-basic-source-listing.md