This may be interesting, “PC DOS 1.1 From Scratch” by Michal Necasek (OS/2 Museum). Especially for anyone interested in / fighting with the tool chains of the day…
A number of years ago, the Computer History Museum together with Microsoft released the source code for MS-DOS 1.25 (very close to PC DOS 1.1) and MS-DOS 2.11. I never did anything with it beyond glancing at the code, in no small part because the release was rather poorly organized.
Now I finally decided to look at the code for DOS 1.1 and see how far I could get with it. For both DOS 1.1 and 2.0, there are ‘object’ and ‘source’ directories.
I was able to put together a bootable 320K floppy running something very close to PC DOS 1.1 with source code and tools that allow rebuilding
COMMAND.COM. Batch files (
MKCOM.BAT) are provided to simplify the effort. Everything is done “in place” with very little room left on the disk.