BASIC interpreter

A BASIC interpreter is an interpreter that enables users to enter and run programs in the BASIC language and was, for the first part of the microcomputer era, the default application that computers would launch. Users were expected to use the BASIC interpreter to type in programs or to load programs from storage (initially cassette tapes then floppy disks).

BASIC interpreters are of historical importance. Microsoft's first product for sale was a BASIC interpreter (Altair BASIC), which paved the way for the company's success. Before Altair BASIC, microcomputers were sold as kits that needed to be programmed in machine code (for instance, the Apple I). During the Altair period, BASIC interpreters were sold separately, becoming the first software sold to individuals rather than to organizations; Apple BASIC was Apple's first software product. After the MITS Altair 8800, microcomputers were expected to ship bundled with BASIC interpreters of their own (e.g., the Apple II, which had multiple implementations of BASIC). A backlash against the price of Microsoft's Altair BASIC also led to early collaborative software development, for Tiny BASIC implementations in general and Palo Alto Tiny BASIC specifically.

BASIC interpreters fell from use as computers grew in power and their associated programs grew too long for typing them in to be a reasonable distribution format. Software increasingly came pre-compiled and transmitted on floppy disk or via bulletin board systems, making the need for source listings less important. Additionally, increasingly sophisticated command shells like MS-DOS and the Apple Macintosh GUI became the primary user interface, and the need for BASIC to act as the shell disappeared. The use of BASIC interpreters as the primary language and interface to systems had largely disappeared by the mid-1980s.