The AppleIIGS is the fifth and most powerful model of the Apple II family. It is a 16 bit computer using the 16-bit 65C816 Microprocessor. This processor gives direct access to megabytes of RAM, and the mouse. This enabled Apple to equip the computer with a color graphical user interface, and an Apple Desktop Bus interface that was used for Mouse, keyboard and other input devices.

The sound capabilities were also greatly improved using a wavetable synthesis chip from Ensoniq

The Apple IIGS came standard with 256KByte of memory, and was expandable to 8MByte. The computer supported a 12-bit palette in 320x200 or 640x200.

The W65C816, or 65816 for short, is an 8/16 bit microprocessor developed by the Western Design Center (WDC). The W65C816 is an enhanced version of the WDC 65C02 8-bit processor, which itself is an enhancement of the MOS 6502. The W65C816 was the CPU for the Apple II gs and, in slightly modified form, for the Super Nintendo Entertainment System.

The Processor has selectable 8- and 16-bit register sizes. In addition to the 16-bit registers, the processor also extended memory addressing to 24 bits, supporting memory sizes up to 16 MByte. Other improvements were an enhanced instruction set and a 16-bit stack pointer.

The W65C816 starts in emulation mode, in which it behaves like a 65C02. The processor can then be switched to native mode with a two instruction sequence, causing it to enable all the new features, while also maintaining backwards compatibility with most 65C02 code.