older OS

I used Workbench 3.1 , which was the OS used by Amiga 500s.
It was very much like a Mac OS in that when you put in a dik it appeared on the desktop.
One real difference was that it was a real WIMPS environment. ie windows icons menus pointers screens. You could run a program in a window like you do today with word or excel and swithc between them. Some programs used screens so the bar across the top of the screen like on a Mac with the menu options could be dragged down and another screen would be under it if such a program was running in the background.
The mouse had 2 buttons… at a time when many PC mouses had 2 or 3 but rarely used more than one.
The left button was a select button and the right mouse button was the menu button (with a little program called popupmenu you could access menus with the pointer anywhere on the page or window, though without that program running (which was not part of the OS) you had to move the mouse up to the menu bar)

No hard drive, 512K of RAM and one 880K floppy… and much better graphics than IBMs of the day… it was the Playstation 2 of the day (with the Atari ST being like a Nintendo 64).
At the time the graphics on IBM games was pitiful… usually 16 colours only.

When I was little, in the early 80’s I had some kind of portable computer which used TRS-80 (which is actually a programming language, a version of Basic) but it was also the OS. Strange… Anyways I don’t remember hardly anything about it.

Got some skills in RMB and Pascal WS from HP

I could add DOS, and VMS.