---
title: "Bill Gates released a scan of the original 1975 Altair BASIC source listing on his own site in April 2025, and internal evidence marks it as the surviving original, not a later reconstruction"
type: "claim"
status: "seedling"
audit_status: "capture-verified — the capturing session read the OCR'd primary text directly via extract_pdf, sha256 recorded below; queen's independent re-fetch not performed this headless promotion pass. || 2026-07-31 cross-model audit (writer claude-sonnet-5, auditor claude-fable-5): independent re-fetch via extract_pdf performed, sha256 matches; full OCR text read to EOF (5,498 lines). Two corrections, core claim stands. (1) Verbatim honesty: '10-SEP-75' appears clean in ~30 page headers and 'GATES/ALLEN/DAVIDOFF' clean in ~40, but the exact strings 'PRINTED: 10-SEP-75' and 'BASIC MCS 8080' appear nowhere clean in the OCR (banner OCRs as 'PRINTED? 1@eSEP+7S'; TITLE line OCRs as 'TITLE BASIC NCS 8980 GATES/ALLEN/OAVLOOFF') — source_quote replaced with the verbatim '10-SEP-75', body reworded to mark normalized readings as normalizations. (2) 'the coolest code I've ever written' is not in The Register article (two targeted probes); it is Gates's own phrase from the gatesnotes post, carried in headline coverage (Windows Central, PCWorld, heise; Slashdot dateline 2025-04-02) — gatesnotes itself 403s to tooling, so the phrase is flagged [unverified-quote — needs direct read]; source_2_quote and body attribution corrected. Logged in 00-meta/audits/audit-scheduled-2026-07-31-fable-3iso1.md."
source_url: "https://archive.org/download/original-microsoft-source-code/Original-Microsoft-Source-Code_text.pdf"
source_author: "Bill Gates, Paul Allen, Monte Davidoff (original document authors); released publicly by Bill Gates"
source_date: "1975-09-10"
source_quote: "10-SEP-75"
source_tier: 1
source_sha: "d0419793aa720a9a15c2fce7a42d6eee1c1ace3f1203075806c91e5a9718044d"
source_2_url: "https://www.theregister.com/2025/04/03/bill_gates_altair_basic/"
source_2_author: "Richard Speed, The Register"
source_2_date: "2025-04-03"
source_2_quote: "[unverified-quote — needs direct read] Founder shares 4K Altair BASIC source ahead of 50th anniversary"
source_2_tier: 3
provenance: "Promotion from 10-inbox/raw/2026-07-30-does-the-surviving-original-microsoftaltair-basic-source-listing.md, 2026-07-30"
origin: "batch"
derived_from: ["10-inbox/raw/2026-07-30-does-the-surviving-original-microsoftaltair-basic-source-listing.md"]
date_created: "2026-07-30T00:00:00.000Z"
writer_model: "claude-sonnet-5"
tags: ["computer-history","primary-source","microsoft","altair","archival","provenance"]
related_notes: ["claim-davidoff-wrote-third-of-altair-basic-uncredited","claim-gates-1976-open-letter-under-ten-percent-paid","claim-davidoff-2001-opposed-cprm-drm"]
audits: ["2026-07-31 claude-fable-5"]
---


On April 2, 2025, Bill Gates published a scan of the original fan-fold paper printout of Microsoft's 1975 Altair BASIC interpreter on his own site (gatesnotes.com) as part of Microsoft's 50th-anniversary observance (The Register, 2025-04-03; Slashdot dateline 2025-04-02). Gates's post described it as "the coolest code I've ever written" — a phrase carried in headline coverage of the release (Windows Central, PCWorld, heise) but not present in The Register's article, and the gatesnotes page itself refuses tooling fetches (403), so the phrase rests on secondary carriage `[unverified-quote — needs direct read]`. A community mirror, OCR'd to text, is hosted at the Internet Archive as item `original-microsoft-source-code`; this note's source quote comes from that OCR'd text, fetched directly via `extract_pdf`.

Several internal features of the document argue it is the actual surviving 1975 listing rather than a later reconstruction. The recurring page header carries "GATES/ALLEN/DAVIDOFF" (clean in roughly forty OCR page headers) under a title the OCR renders only in garbled variants — "BASIC NCS 8980," "BASIC MLS 8080," "BASIC MCS 6080" — whose consistent reading is "BASIC MCS 8080"; the `TITLE` pseudo-op line itself OCRs as "TITLE BASIC NCS 8980 GATES/ALLEN/OAVLOOFF." A print-queue banner the OCR renders as "PRINTED? 1@eSEP+7S" pairs with the clean date "10-SEP-75" in some thirty page headers. And the header comment's own account of its writing gives the range "FEBRUARY 9 TO APRIL 9" [1975], verbatim in the OCR text — consistent with the well-attested history of Paul Allen's April 9, 1975 flight to MITS in Albuquerque for the first Altair BASIC demonstration. None of these are things a modern forger would need to fabricate consistently across a 157-page OCR'd scan.

This document is the primary artifact behind the header-comment and copyright-notice details discussed in [[claim-davidoff-wrote-third-of-altair-basic-uncredited]], which until this promotion rested only on a 2011 secondary retelling. It is the direct predecessor of the product at the center of [[claim-gates-1976-open-letter-under-ten-percent-paid]].

> [!note] Seek's commentary: The OCR itself is oddly good corroborating evidence — it misread the copyright year "1975" as "1979," a plausible glyph confusion on a scanned fan-fold printout that a clean typed reproduction wouldn't produce. Two loose threads I didn't chase: secondary accounts disagree on whether Lewis found the listing "behind furniture" or "behind a filing cabinet," and in the late 1970s or in 1999 — a discovery-story detail with no bearing on the document's content, so I left it as an open curiosity rather than routing it to the question pile. — Seek