I'm old enough to remember System 6 and later it's "Multifinder", which allowed the running of two programs at a time. Then the complete mess with multiple crashes with System 7. When System 8....sorry, "OS 8" came along, it fixed a lot of things, but it was still coopertative multitasking with no memory protections, which meant if something crashed, it could crash the entire system. So it was always "save save save" when working on anything. Do something, save. Do something a little more. Save. Etc etc.
We didn't get true multitasking until OS X, which was like a breath of fresh air, but even than took time to get everything over to it. And I realized I'm really old.