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).
From the video [1] that links to Ben Eater's fork with extensions and configuration specific to his 6502 breadboard computer [2]. That in turn is forked from `mist64/msbasic` which refers to a blog post [3] which states:
> This episode of “Computer Archeology” is about reverse engineering eight different versions of Microsoft BASIC 6502 (Commodore, AppleSoft etc.), ...
> This article also presents a set of assembly source files that can be made to compile into a byte exact copy of seven different versions of Microsoft BASIC, and lets you even create your own version.
So Ben Eater's version is based on a reverse engineered version of the same program. You should be able to adapt the code released here to run on Ben Eater's 6502 with a bit of work.
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?
It would also be interesting why it was open-sourced now. I assume if they had done the same last year, the resulting loss of revenue would not have destroyed the plucky little $3T upstart.
I have a copy of "Tiny" Pascal by Supersoft from 1979 on a cassette tape which was licensed to Tandy Corp and which would load onto a 16KB TRS-80 Model III and allow a bit of room for programming.
One of the great regrets of my life is that when I was doing so and when it would have mattered, I was unaware of the patch for this which would have allowed it to be saved as an executable to a TRS-DOS disk....
Microsoft itself popularized BASIC on microcomputers with its 8080 BASIC, starting on the Altair and ported to everything with A, B, C, D, E, H, and L registers since.
Before then, however, BASIC was already popular on minicomputers as both an introductory language for beginners and a business language; the various "Business BASIC" dialects providing a small-business alternative to COBOL on mainframes with their features for decimal math and ISAM database access.
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.
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)
[1] https://www.youtube.com/playlist?list=PLowKtXNTBypFbtuVMUVXN...
> This episode of “Computer Archeology” is about reverse engineering eight different versions of Microsoft BASIC 6502 (Commodore, AppleSoft etc.), ...
> This article also presents a set of assembly source files that can be made to compile into a byte exact copy of seven different versions of Microsoft BASIC, and lets you even create your own version.
So Ben Eater's version is based on a reverse engineered version of the same program. You should be able to adapt the code released here to run on Ben Eater's 6502 with a bit of work.
[1] https://www.youtube.com/watch?v=XlbPnihCM0E&list=PLowKtXNTBy...
[2] https://github.com/beneater/msbasic
[3] https://www.pagetable.com/?p=46
https://www.folklore.org/MacBasic.html
I have a copy of "Tiny" Pascal by Supersoft from 1979 on a cassette tape which was licensed to Tandy Corp and which would load onto a 16KB TRS-80 Model III and allow a bit of room for programming.
One of the great regrets of my life is that when I was doing so and when it would have mattered, I was unaware of the patch for this which would have allowed it to be saved as an executable to a TRS-DOS disk....
Before then, however, BASIC was already popular on minicomputers as both an introductory language for beginners and a business language; the various "Business BASIC" dialects providing a small-business alternative to COBOL on mainframes with their features for decimal math and ISAM database access.