(Not development in C)

I've used FreeDOS for doing BIOS updates. In the pre-UEFI days it was common for manufacturers to provide BIOS updates as a DOS executable, apparently with the expectation that the customer would be able to dig up some old MS-DOS disk somewhere.

I suppose nowadays there isn't much use for that anymore thanks to doing FW updates via UEFI capsules. Though at least on the Linux side (LVFS/fwupd) it seems most PC clone vendors aren't on board yet.