Microsoft open-sources Bill Gates’ 6502 BASIC from 1978

In a significant move to honor computing history, Microsoft has made the complete source code for Microsoft BASIC for the 6502, Version 1.1, publicly available. This interpreter, dating back to 1978, played a crucial role in the early days of personal computing, powering iconic machines such as the Commodore PET, VIC-20, Commodore 64, and Apple II through various adaptations. The company shared an impressive 6,955 lines of assembly language code on GitHub, under an MIT license, enabling developers and enthusiasts to freely use, modify, and distribute this foundational code. Bill Gates, in a blog post from 2010, reflected on the creation process, stating, "Rick Weiland and I wrote the 6502 BASIC... I put the WAIT command in." For countless individuals in the late 1970s and early 1980s, variations of Microsoft's BASIC provided their initial foray into programming. Users were able to run simple commands like "10 PRINT 'HELLO'" and "20 GOTO 10," generating endless loops of text on their screens—often their first opportunity to interact directly with a computer. The BASIC interpreter was essential in translating easily understandable commands into machine-executable instructions, one line at a time. Despite its brevity, the 6,955 lines of assembly language in Microsoft's BASIC communicated directly with the processor, showcasing remarkable efficiency. This was particularly important during an era when RAM was extremely costly. The MOS 6502 processor that ran this BASIC was priced around $25, in stark contrast to competitors' chips that sold for approximately $200. Chuck Peddle, the designer of the 6502, aimed to democratize computing, leading to widespread adoption in devices like the Atari 2600 and the Nintendo Entertainment System. In 1977, Commodore secured a licensing deal with Microsoft for a flat fee of $25,000, granting them perpetual rights to use the software in an unlimited number of machines without ongoing royalties. Although $25,000 was a significant amount at the time, Commodore ultimately sold millions of computers featuring Microsoft BASIC. The released version, labeled 1.1, incorporates bug fixes that were collaboratively implemented by Commodore engineer John Feagans and Bill Gates during a visit to Microsoft in 1978. Among the enhancements are memory management improvements—known as "garbage collection" in programming—which later shipped as "BASIC V2" on the Commodore PET.