When you have only 16KB of memory, you can’t afford to waste any of it on fluffy stuff

The original IBM PC came with 16KB of memory. That's not a lot of space in which to squeeze an operating system, especially since you had to leave enough memory for the user to actually get work done. A product of its time, the MS-DOS kernel is written entirely in assembly language, pretty much standard procedure for programs of the era. It also...