Here’s some pretty unexpected news. Although it may not have much practical use today, it carries a lot of historical significance. So, let’s get straight to the point.
In an unexpected move, Microsoft has just opened up the full source code for its legendary 6502 BASIC interpreter, one of the earliest products the company ever shipped. The release, published on GitHub, covers version 1.1 of the interpreter, which dates back to 1976 and was later modified in 1978.
The code was originally developed by none other than Bill Gates himself and Ric Weiland, containing 6,955 lines written in assembly, compact enough to fit in an 8K space, for the MOS Technology 6502 processor – the same chip that powered early machines like the Apple II, Commodore PET, and Atari 2600.
In 1977, Commodore paid $25,000 for the rights to bundle the interpreter with its systems, a move that helped establish BASIC as the entry point for a generation of programmers.
Of course, this isn’t the first time copies of the code have surfaced, but until now, there hadn’t been an official release from Microsoft under a modern license. Preservationists had already done the work of reconstructing the build environment and verifying that the binaries matched the original ROMs.
According to Microsoft’s official announcement:
“For decades, fragments and unofficial copies of Microsoft’s 6502 BASIC have circulated online, mirrored on retrocomputing sites, and preserved in museum archives. Coders have studied the code, rebuilt it, and even run it in modern systems. Today, for the first time, we’re opening the hatch and officially releasing the code under an open-source license.”
Okay, what’s the point of all this in 2025? In short, the release has value for retrocomputing enthusiasts, emulator developers, and FPGA projects that aim to recreate the experience of these early systems. Plus, Microsoft has essentially handed over a piece of computing history that anyone can study, modify, or rebuild.
So, the repo is there, legally clear, and technically rich. There’s no guesswork—just real, usable code from the dawn of personal computing. Even if it doesn’t make a lot of practical sense today, it’s still a smart move by Microsoft.
It gives younger users a glimpse of what was considered cutting-edge 50 years ago—just under 7,000 lines of assembly code that helped shape computer history.
