Microsoft's 6502 BASIC is now Open Source (2025)

In 1979, I made a program called VisiBase in this BASIC. It's a visual database modeled after VisiCalc. That won me a joystick in at a competition by the local computer store. :-) Still have the source, that works in an Apple 2 emulator. It's 13 K in ASCII (untokenized).

Ben Eater's 6502 series [1] uses MSBASIC for programming along with WozMon as the terminal interface.

[1] https://www.youtube.com/playlist?list=PLowKtXNTBypFbtuVMUVXN...

Previous discussion:

Microsoft BASIC for 6502 Microprocessor – Version 1.1 - https://news.ycombinator.com/item?id=45118392 - Sept 2025 (198 comments)

Related ongoing thread:

Microsoft open-sources "the earliest DOS source code discovered to date" - https://news.ycombinator.com/item?id=48253386 - May 2026 (110 comments)

Sadly nothing in Scott's blog post about how they obtained the source. Was it still in Microsoft's archives? Did they happen upon some tractor-feed print-outs they had to type in by hand?

The Apple ][ basic interpreter placed its "get next token" routine down in the first 255 bytes of the computer's memory. Being there allowed for the machine instructions to be fetched twice as fast as "high memory". And "get next token" is definitely a good guess for hotpath.

Maybe Apple can finally release MacBasic now that Microsoft can no longer stop licensing their Basic to the Apple II family.

I doubt the .gitignore, README.md, and SECURITY.md files were created 49 years ago, as the GitHub repo indicates :D

Do you think computing history would have been much different if Microsoft made a 6502 Pascal interpreter instead?

I am really torn about this. Sure Microsoft is doing a lot of open source today (.NET core, VS Code and a bit of historic curiosities such as this one) but the "open letter to the hobbyists" still stands :) Release the Windows source code then we are talking.

[dead]