man, running on 4 hours of sleep is killing me.
I can't even remember the MS-DOS interrupt to open a file!

I know reading it is int 21 ah=3f, closing it is int 21 ah=3d, and I'll never forget that seeking is int 21 ah=42, but how do you open a file?
I mean, not the int 21 ax=6c00 way, that one is only for DOS 4.0+, and obviously a game released in 1990 isn't gonna use that.

ahh, now that I've looked it up, it seems I was wrong!
closing isn't 3D, that's 3E! 3D is open!

no wonder I couldn't remember it, I had it confused with another call

looking it up took less than 10 seconds, but that's 10 seconds I'll never get back.

what the fuck do you mean that carmen.dat is opened on the first call to finish_draw_maybe()?

like, I know there's a "maybe" in that name, but it's not THAT big of a maybe.

oh thank god, that was a bit of confusion from manually tracking stack frames.
it actually LoadDatFile, which makes a HELL of a lot more sense

darn. Compiler Explorer doesn't support MS C Compiler 5.1 from 1988. Guess I gotta spin up an emulator again

the annoying thing is that MS C Compiler 5.1 is the most mundane-ass DOS application. If I had a 32bit windows install rather than 64bit, it would probably just run natively on my system

I'm gonna build an m.2 addon that's just a drop in x86 coprocessor. I know a lot of computers that could use an x86 processor these days.

it's like a Super Game Boy, but for your PC! Plug in this extra hardware, and now your system is compatible with a ton more software!

note to self: figure out how Ghidra fidb works, so I can apply it to MSC5.1 (which was sadly overlooked by the developers of ghidra)

note to self:
maybe do it for everything MS-DOS.

okay don't change that byte, GOT IT.
I think I failed to load the cursor, which caused it to corrupt the mouse cursor catastrophically

a fun kind of reverse engineering tactic that I practice probably more than I should is a version of The Scream Test (which is the principle that the easiest way to find who "owns" a server is to turn it off and see who screams): if you don't know what some code does, break it. and see what screams.

I think I may have found unused graphics for a feature that'd change the Acme Detective Agency at the beginning to be season-specific. There's summer, fall, winter, and spring variants, but the game seems to be hardcoded to summer

no, this should be working. Hmm. Maybe they just missed one of the four images?

nope! it's fully functional, based on the system date.

I did a little looking into the contents of MIDISND.DAT

It's got 12 small tracks, and each of them is a valid MIDI file if you remove the first byte.

heh. I was checking different near-death animations by overriding the randomness, so I had to tell my debugger to set AX to 0

guess which animation that is? The one with the AXe.

why do they store the day of the week as a 16bit int?

future proofing in case the calendar gets updated and has more than 256 days in the week?

I accidentally applied a patch backwards and put the detective to sleep, forever.
They're in Rome and they've just slept through about two months of nothing