Remember, UNIX was originally developed on a DEC PDP-7 to multiuser+multitask in 1969; The PDP series (oddly they were 18-bit'ers) had had a very similar instruction set with the MOS 6502
As a side note: Compute! Magazine published a simple multitasking piece of code that used the NMI (Non-Maskable Interrupt) vector to do it on a C64; one of my early efforts changed the Basic start/end vectors to but Basic in that top 4K meant for ml programs leaving the 32K below it as free ram. It was for a BBS Terminal program that put downloads in the large buffer away from the code..
Did anybody remember the Mac OS's early version of a task switcher that went from task to task by clicking a button?
Sorry about this post, my ADD is showing
