Before macOS, and before OS X, there was just Mac OS. This is often referred to as “Classic” Mac OS. It includes System 1 all the way up to Mac OS 9.x. I started using a Mac with System 6 on a Macintosh Classic. Then I moved up to a Macintosh IIsi running System 7. Finally, after the PowerPC transition, I used a Power Macintosh 8500 which ran all of the later versions of “Classic” Mac OS. I was recently having a conversation with another developer who grew up using Macintosh computers...
