BASIC extension

BASIC toolkits - not to be confused with widget toolkits - were a common type of program in the 1980s 8-bit home micros. They added additional features to the built-in BASIC interpreter.

Toolkits ran as terminate and stay resident extensions to the BASIC interpreter supplied with the machine. At the time, such interpreters almost always came programmed into the ROM of the computer, making it impossible to modify or patch the code. It was also extremely rare for manufacturers to offer upgrades or bugfixes except as part of new models of machine. Typical toolkit functionality were editing extensions, such as commands to renumber a program, perform block line deletions and so on.

As the original language was held in immutable ROM, it generally was difficult for a toolkit to directly extend the language, except by adding new keywords to perform functions not implemented by the original interpreter. For example, the Lightning BASIC toolkit extended the Amstrad PCW's Mallard BASIC language with many new facilities - see the Mallard BASIC article for details.

The Beta BASIC extension to Sinclair BASIC on the ZX Spectrum computer started out as a simple toolkit but grew into an interpreter in its own right.