Or 128K of ram and 400 kb disk for that matter.
That said, OSs came with a lot less stuff then.
Sure we could go back... Maybe we should. But there are lots of stuff we take for granted to day that were not available back then.
It's hinted at in this tutorial, but you'd have to go through the Programmer's Reference Manual for the full details: https://www.stevefryatt.org.uk/risc-os/wimp-prog/window-theo...
RISC OS 3.5 (1994) was still 2MB in size, supplied on ROM.