Writing a DOS Clone in 2019
4 comments
·November 3, 2025tombert
PeaceTed
I mean DOS is essentially just the frame work between the software and the BIOS/hardware. Once code is running the OS isn't doing too much.
In that sense DOS programs run without any guard rails. Video memory is just a memory address where you can throw data in and it shows up on screen, but it also means that any kind of memory pointer issue can write over almost anything in RAM. It was trial and error to ensure everything worked and seeing as machines were not always online, there was a much smaller risk of security issues being leveraged.
lloydatkinson
I feel like the article is just too short for the given topic. So much more detail could have been added.
forgotpwd16
There's a follow up post and there was supposed to be another one too but apparently was never written. Regarding code:
>Once I return to work and get approval to open up the source code, I’ll make the repo public as well.
Guess approval wasn't given?
I have thought about doing this. I have no idea what would be involved, but given how many DOS-compatible OS’s were around in the 1980’s it must be comparatively easy to build than other operating systems.
I remember playing with Caldara OpenDOS and Concurrent DOS years ago, and it always seemed like it might be fun to make my own.