Some related stuff:

In 2004, Gavin Barraclough’s mini-OS [0] won the IOCCC, packing a 32-bit multitasking operating system for x86 computers, with GUI and filesystem, support for loading and executing user applications in ELF binary format, with PS/2 mouse and keyboard drivers, VESA graphics, a command shell, and an application into 3.5 KB of highly obfuscated C code.

In 2021, Justine Tunney wrote SectorLISP [1], a Lisp implementation that fits into a bootsector and is able to run McCarthy’s metacircular evaluator.

[0]: https://www.ioccc.org/2004/gavin/index.html [1]: https://github.com/jart/sectorlisp

Two questions:

1. I just saw how str_print is implemented. It's so short even though it's asm. Is this why nul-terminated strings were so popular and became the default in C? Would pascal strings be much longer/uglier/harder in asm?

2. Why is str_print repeated in multiple files? How would you do code sharing in asm? I assume str_print is currently not "static" and you'd have to make it so via linking or something, and then be able to get its address using an asm macro or something?

Very cool! I have to ask: what would the total size be if the package included the bios functions?

Also: what could be done if the size limit were 8kbyte like the mask-rom bios days?

Thanks for pointing me towards the bosh emulator.

I have a more general question - what is the minimum that is needed to qualify as an operating system? Is there something agreed on generally? Searching operating system minimum requirements leads to the wrong kind of info for me....

BIOS is underrated. Basically the driver portion of a DOS- (or CP/M)-like operating system. As demonstrated, you don't need to add too much to it (program loader, simple file system, maybe a command shell and system utilities if you are ambitious) to get a functional mini-DOS.

Well that's cool. Does the name stand for something?

On projects like this, where the IMG is small enough, I would think it was ideal to include osle.img with the zip.

cool stuff, like you still fit quite a bit in there too, 510 bytes can be tricky.

if you want an ahci controller to 'see' it, it will need partition table too, which will make it even less bytes (or maybe cleverly encoded)

All professors should be doing this decades ago right ?