It was virtually identical to the previous Macintosh, differing primarily in the amount of built-in random-access memory.

The increased memory turned the Macintosh into a more business-capable computer and gained the ability to run more software.

Models with the enhanced ROM also supported Apple's Switcher, allowing cooperative multitasking among (necessarily few) applications.

The 512K was the oldest Macintosh capable of supporting Apple's AppleShare built-in file sharing network, when introduced in 1987.

The expanded memory in the 512K allowed it to better handle large word-processing documents and make better use of the graphical user interface and generally increased speed over the 128K model.

Apple offered an upgrade kit which replaced the floppy disk drive and ROMs, essentially turning it into a 512Ke.