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IIgs GS/OS

Introduced: September 1986
Terminated: December 1992

The IIgs was the last and most powerful Apple II. The IIgs was a quantum leap ahead of the earlier IIe or IIc form factors. It represents the last of the II line and an attempt to keep it going just a little while longer. Woz himself contributed to its design and later lent his name to the "Woz Special Edition IIgs" of which Apple produced about 50 thousand units (all other variants probably amounted to hundreds of thousands produced). The IIgs had a true GUI OS very similar to the MacOS. It was a 16-bit computer while the earlier IIe and IIc were 8-bit computers. Also available for use with the IIgs was a 16-bit version of ProDOS, which was a vamped-up version of the older 8-bit ProDOS used in the earlier Apple II's.

The IIgs introduced ADB (Apple Data Bus), which later found its way to the Macintosh platform. ADB is similar to PS2 used in the PC (Wintel) line of computers. ADB added quite a bit of functionality to the system and was used to connect the keyboard, mouse, or other peripherals. Unlike PS2, it is "hot-swappable". Apple used ADB on all Macintosh models until it was replaced with USB on the original iMac model in 1998, a move that Wintel makers later followed. All Apple products now use USB exclusively for the mouse and keyboard channels.

The IIgs also shipped with a powerful BASIC compiler. Previous II's used an interpreter, primarily because it tasked the system less and was easier to design in the original Apple II firmware. Compilers allow programs to run much quicker because the whole program is "compiled" into an executable before running. Interpreters read programs line-by-line, never creating a singular executable program. Although much easier to debug, an interpreter runs programs much slower. Programmers had to use special tricks or techniques with the old Applesoft BASIC interpreter to get the most out of it. IIgs BASIC provided many more options and command words than the earlier Applesoft BASIC due in no small part to the increased capabilities of the hardware.