GW-Basic Source Notes
os2museum.com
os2museum.com
Of course, this is all speculation.
https://github.com/tkchia/GW-BASIC
"All files can now be assembled with Microsoft MASM 5.1A."
"The interpreter is semi-working, but some parts of the platform-specific support code are still missing or incomplete."
Before that I would tinker with Applesoft BASIC on a IIe my father brought home from Rockwell Collins... BASIC was/is such an approachable dialect for kids.
After a few years tinkering I graduated to Pascal and C/C++ after an uncle unloaded all of his old Borland books on me. If it wasn't for BASIC teaching me programming fundamentals (variables, conditions, loops, "functions", etc) I don't think I would have been able to grok formal/more-powerful languages. At first I didn't have any resources/mentors/Google for programming so I really needed BASIC.
BASIC will always hold a special place in my heart!
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..But works in Firefox
There's a reason nobody writes large programs in assembler anymore (except for the IRS)
That's why you see in the source code the phrase "This translation created on...". Microsoft, at this time, hasn't made available the tools they used to generate this code or the original version it was created from.
[1] https://devblogs.microsoft.com/commandline/microsoft-open-so...
This also seems corroborated in the dev blog you link, though without source control history, the upstream translation layer, and the original "intermediate assembly" code, the details at this point are relatively fuzzy.