Someone recommended a nice (German) talk:

https://media.ccc.de/v/ds24-394-linux-hello-world-nur-mit-einem-hex-editor

Luckily, everything™ is easier™ on DOS with .COM files. A fun little time killer to make a HELLO.COM using only a hex editor, the Intel docs and the DOS interrupt list.

That ModR/M stuff is easy in the end, but it took me quite some time to understand it. 🥴

(I’m still new to DOS on this level and didn’t know that all segment registers are initialized to the same values, apparently, so copying CS to DS was not necessary. Too lazy to update the screenshot. File size shrinks by 4 bytes.)

https://movq.de/v/0139fbaabc/doshello.png

@movq@www.uninformativ.de Interesting, it’s always good to know how things work under the hood. But I’m very glad, that I do not have to deal with this low-level stuff. :-)

@lyse@lyse.isobeef.org Yeah, it’s different for everone. 😅 I, for one, am not particularly interested (yet) in the underlying hardware. Logic gates and stuff like that, that’s not my kind of thing. Maybe in the future, but there’s still more than enough to explore in the world of software. 😃

I might actually end up doing this excercise with our apprentices at work. You can use this as a starting point to teach a ton of things. 🤔