Monte Davidoff wrote the floating-point math package — roughly a third — of the original Microsoft BASIC, was named in the source comments, and was left off the copyright notice

The original Microsoft (then "Micro-Soft") BASIC interpreter for the Altair 8800 was written by three people, and the program's own header comment said so: "PAUL ALLEN WROTE THE NON-RUNTIME STUFF / BILL GATES WROTE THE RUNTIME STUFF / MONTE DAVIDOFF WROTE THE MATH PACKAGE." Davidoff, a Harvard undergraduate, contributed the floating-point math routines — down to an assembly-language ARCTAN implementation.

Harry Lewis, who taught Gates at Harvard and had direct knowledge of the PDP-10 account on which the interpreter was developed, later tallied the listings and put Davidoff's file at "about 31 pages" of a roughly 65-page program — a little under half by line count, and "roughly a third" as the capture frames the whole contribution. Yet, Lewis writes, Davidoff was "acknowledged by them but not included on the copyright notice." The credit that appeared in the code comments did not carry over into the legal authorship claim on the product.

This is a credit-misattribution case in the vault's commercial-software domain rather than its academic-priority domain. It sits beside claim-ann-hardy-tymshare-os-miscredited-to-husband (authorship credit for built work, misdirected) and the algorithmic-priority cluster around claim-linnainmaa-priority-not-paternity, myth-werbos-invented-backpropagation, and claim-parker-1985-technical-report-not-cited. The failure mode is the same — real work with the wrong (or missing) name attached — but the mechanism here is a copyright notice, not a citation.

The claim rests on Lewis's secondary analysis (Tier 2), not on the surviving BASIC source listing itself. The original source is said to survive in Gates's 2004 donation to Harvard, so a primary check is possible; it is routed to question-verify-davidoff-altair-basic-source-header-primary. The note stays status: seedling until that listing is read.

Update 2026-07-30

A second capture read the surviving primary listing directly — Bill Gates's own April 2025 release of the scanned 1975 fan-fold printout, OCR'd text fetched via extract_pdf (Internet Archive item original-microsoft-source-code; see claim-gates-2025-released-original-1975-altair-basic-source-scan). Both of Lewis's central claims check out verbatim against the primary artifact: the header reads "MONTE DAVIDOFF WROTE THE MATH PACKAGE," and the copyright line immediately above it names only "BILL GATES AND PAUL ALLEN." (The OCR misread the year as "1979"; the document's internal writing range and every secondary account agree it is 1975.) This upgrades the note's two central facts from Tier 2 (Lewis's retelling) to Tier 1 (the artifact itself). The one figure still not checked against the primary is Lewis's "about 31 of 65 pages" estimate — the capture did not tally page boundaries — so "roughly a third" in this note's title remains a Tier-2 figure, and the note stays seedling on that basis. question-verify-davidoff-altair-basic-source-header-primary has been updated to reflect exactly this split.