Multitasking: we all do it. For a feature of modern computing multitasking has surprisingly old roots. It started out as timesharing on vacuum tube based machines, reached ubiquity on large computers, then hit a wall: the microcomputer. Multitasking didn't smoothly transition over as soon as home computers hit the scene. It took some time, and it took some adaptation. Today we are looking at what made timesharing work, early changes to microprocessors that paved the way for multitasking, and one of the first operating systems to support timesharing in the home.   Selected Sources:   https://www.roug.org/soren/6809/os9sysprog.html - OS-9 System Programmer's Manual   https://archive.org/details/byte-magazine-1979-01/page/n15/mode/2up - Article on the development of the 6809   https://sci-hub.se/10.1109/TEC.1962.5219356 - The One-Level Storage System