When I was nine years old, I liked poking around with a hex editor on my dad’s PC.

I didn’t speak English and MS-DOS wasn’t yet localized to Finnish in 1989, so I decided to try translating it myself with a dictionary by manually finding and replacing strings in the SYS/COM files. The result worked and my dad was suitably impressed, if probably a bit peeved that nothing worked anymore in the shell as expected (since I had replaced all the basic command names too — “dir” became “hak” and so on).

It’s pretty cool to see those strings again in src/MESSAGES.

At the same time, it feels a bit sad that today’s kids can’t get the same feeling that the computer is really theirs to modify. Modern operating systems don’t run binaries tampered with a hex editor. Most kids are on operating systems like iOS where they can’t even run a C compiler.

They can play with code in various sandboxes locally and on the web, but the computer fundamentally belongs to someone else today.

It looks like "brain damaged" was the developer's go-to insult when frustrated :D

2024-04-25 19:35 ~/sort/dl/MS-DOS % grep -nri 'brain[ -]damage' .

./v4.0/src/DOS/STRIN.ASM:70:; Brain-damaged TP ignored ^F in case his BIOS did not flush the

./v4.0/src/DOS/PATH.ASM:24:; MZ 19 Jan 1983 Brain damaged applications rely on success

./v4.0/src/DOS/FCBIO.ASM:28:; MZ 15 Dec 1983 Brain damaged programs close FCBs multiple

./v4.0/src/DOS/FCBIO2.ASM:28:; MZ 15 Dec 1983 Brain damaged programs close FCBs multiple

./v4.0/src/BIOS/MSBIO1.ASM:82:; REV 2.15 7/13/83 ARR BECAUSE IBM IS FUNDAMENTALY BRAIN DAMAGED, AND

./v4.0/src/CMD/PRINT/PRINT_R.ASM:1772: ; See if brain damaged user entered

As Scott mentioned in the blog post, we were able to get this running on one of my original IBM XTs with an original IBM monochrome display adapter and display. It was very cool to be able to switch between a running version of a small game, Turbo Pascal, and a DOS prompt with a single key press.

It is always great to have period software on period hardware!

(added: Short video of it running - https://www.youtube.com/watch?v=YPPNbaQaumk)

I appreciate the work in getting this open sourced but I find it telling that this had to be done through an outside motivator. There seems to be no internal "ticking clock" to get some of these things out in to the open. That's fine no one is owed the source code for this stuff or anything, but it would be nice if there was more interest on the side of the companies to get some of their formative history out so people can learn from it.

Here is a small video of it running on original IBM XT: This was right after we got the floppies read successfully. Serious Kudos to Scott for getting these floppies and the permission to release them!

https://www.youtube.com/watch?v=YPPNbaQaumk