Operating systems today are still marvelous feats of engineering despite their quirks (such as legacy "features" like ANSI and UCS-2 "Unicode" in Windows), the fact that in the past we could fit an entire operating system AND running applications in one megabyte of RAM is remarkable!
Like my sibling poster said, a full megabyte would have been the sheerest luxury. After the ROM was mapped into memory on startup, my C64 had 38 kB available for programs. It is flat-out amazing what people did with that memory, including office software, networking and of course games.
Keep in mind that the Apple II originally shipped with 4 kB.
Everything (including graphics and music) fits in 200kb (177kb exactly)
While it was made almost 10 years ago it is still very impressive.
[1] If you can't or are afraid to run executable (antivirus programs might complain due to compression program they used), here's video of it: https://www.youtube.com/watch?v=KMfyrnu3n_c
As I think back on the hardware, I am amazed that my old C=64 could not only run a word processor, but it could spell check. The machine only had 64 kb of RAM and the disks were so glacial that you couldn't touch them much at all and maintain anything like a usable speed.
The Sinclair Cambridge ZX-80 (sold here as the Timex computer or somesuch) shipped with 1kB of RAM. That said, it wasn't really usable for much beyond programmable calculator kinds of stuff. With a 16kB expansion it was pretty awesome.
My first computer! I was programming in Z-80 assembler, typing in listings from magazines, with no way to save the code. So once the machine was switched off, the program was wiped and it had to be entered again. It's one way to learn the importance of accuracy - after hours of typing hex digits, to have one type cause the program to blow up, and have to start all over.
Q̶u̶e̶u̶e̶ Cue the person looking at source code mentioning something along the lines of "this is real engineering".