This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.
The II and II+ are the computers that launched the Apple II line. They have the 6502 microprocessor, ability to do Hi-res and Lo-res color graphics, sound, joystick input, and casette tape I/O. They have a total of eight expansion Slots for adding peripherials such as the Disk ][ controller, MockingBoard, serial I/O, and printer interface. Clock speed is 1MHz and, with Apple's Language Card installed, standard memory size is 64kB. The distinction between the ][ and ][+ is the installed ROMs. The ] [ starts you in the Monitor program and includes in-ROM Integer BASIC. The ][+ has the AutoStart ROM which tries to locate and boot a diskette upon startup and defaults to Applesoft BASIC which is included in-ROM. Many ][ owners upgraded to the ][+ ROMs. Apple ][ and ][+ computers can run thousands of games, utilities, and other programs created to run under Apple DOS-- chiefly, DOS 3.3. Both machines can, also, run under ProDOS through v1.9 so long as the software does not require features of an "enhanced" 128k IIe. For instance, you can run Appleworks if you have more than 128K RAM installed and a program called PlusWorks. However, the ][ can not run BASIC programs under ProDOS since Applesoft must be in ROM. Recommended configuration: 16K "language card" (in Slot 0), an 80-column video card (not the same as a //e Extended 80-column card), shift key modification (a wire running from shift key to game port), modified character ROMs to display lower case, composite color monitor, Disk ][ controller card, two 5.25" Disk ] [ or compatible drives, parallel printer interface card, and parallell- interface printer. You can add memory beyond 64k in various ways, but many programs that "require 128K" probably will not wor k, no matter how much RAM you have. You can also add accelerators like the SpeeDemon or Rocket/Zip. --Dan DeMaggio, David Empson, Rubywand