IBM BASIC

IBM Personal Computer BASIC, usually called IBM BASIC, is the family of BASIC interpreters that IBM supplied with its Personal Computer, Model 5150, from 1981. IBM did not write the language itself. It licensed Microsoft BASIC and released four versions: Cassette BASIC, held in read-only memory on the machine; Disk BASIC; Advanced BASIC, known as BASICA; and Cartridge BASIC for the PCjr. Beyond the features of an ANSI standard BASIC, the IBM versions supported the graphics and sound hardware of the PC line. Programmers entered source code with a full-screen editor, typed a line number before each statement, and could test expressions at once in immediate mode. Programs were held in a tokenized form in which reserved words became single bytes, and could optionally be saved as plain ASCII text. Disk BASIC and Advanced BASIC shipped with IBM PC DOS up to PC DOS 4, and Microsoft's GW-BASIC is identical to BASICA except that it carries the Cassette BASIC code itself, so it runs on machines without IBM's ROM.