The computers in this line are the Apple II, the Apple //e, Apple //c, Apple //gs, and the Apple III, and finally the Apple IIgs.
The Apple II was a stunning computer, for its day. It had a relatively huge ROM, with lots of utility subroutines, a BIOS of sorts, and (get this) a full, commented source code listing in the manual. The Apple II also had device drivers in ROM on the plug-in cards, so you could actually plug in anything and use it immediately, and an astoundingly inexpensive floppy