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Microsoft BASIC (1975)

The January 1975 issue of Popular Electronics caught the attention of Bill Gates and Paul Allen. On the cover was the Altair 8800 and the headline "World's First Microcomputer Kit to Rival Commercial Models." Allen bought the issue and rushed to Gates's dorm room. They immediately knew this could be their big break.

Within a few weeks they called Ed Roberts of MITS and told him they had a version of BASIC for the Altair — though they still had to build it. Roberts asked when they could demonstrate it. Gates looked at Allen, took a deep breath, and said: "Oh, in two or three weeks." He put down the receiver and turned to Allen: "I guess we should go buy a manual."

Building It

For the next few weeks, Gates and Allen worked day and night. They chose an interpreter to fit everything in 4K — the first appearance of interpreted BASIC. One day in the dining hall, a hesitant voice from the other end of the table called out "I've written some floating-point routines." Marty Davidoff joined the team over lunch.

To pack more power in, Gates and Allen deviated from Dartmouth's eight principles, cramming multiple instructions per line and adding PEEK and POKE commands for direct memory manipulation.

The Final Show

Paul Allen flew to Albuquerque with the paper tape. Halfway into the landing, he realized they had never written a loader program to read the BASIC off the tape. He wrote one in 8080 machine language on scrap paper before the plane touched down.

The machine printed MEMORY SIZE? Allen typed the size, then PRINT 2+2. It printed 4. BASIC worked.

"If we made any mistake anywhere, in the assembler or the interpreter, or if there was something we didn't understand in the 8080, this thing won't work." — Paul Allen, as he flipped the RUN switch

Birth of Microsoft

Gates and Allen had already run a company called "Traf-O-Data" in 1972. In spring 1975 they signed with MITS, referring to their company as "Micro-soft" (for microcomputer software) — a term first used by Gates in a letter to Allen on November 29, 1975. On November 26, 1976, it was registered as "Microsoft" in New Mexico.

Microsoft also became the first victim of software piracy when Gates accidentally left a copy of BASIC on paper tape at a demonstration. In January 1976, Gates wrote his famous "Open Letter to Hobbyists" accusing hobbyists of stealing software. The letter had no effect on hobbyists, but the popularity of BASIC kept growing.

"Nothing would please me more than being able to hire ten programmers and deluge the hobby market with good software." — Bill Gates, "An Open Letter To Hobbyists"