Atari ST BASIC (or ST Basic) was the first dialect of BASIC that was produced for the Atari ST line of computers. It was bundled with all new STs in the early years of the ST's lifespan, and quickly became the standard BASIC for that platform. However, many users disliked it, and improved dialects of BASIC quickly came out to replace it. ST BASIC became famous for its abundance of bugs. It was possible to crash ST BASIC with the following line of code:
Atari commissioned MetaComCo to write a version of BASIC that would take advantage of the GEM environment on the Atari ST. This was based on a version already written for Digital Research called DR-Basic, which was bundled with DR's CP/M-86 operating system. The result was called ST BASIC. At the time the ST was launched, ST BASIC was bundled with all new STs. A further port of the same Basic called ABasiC ended up being supplied for a time with the ST's bitter rival, the Amiga.
The user interface consisted of four windows. An edit-window in which one could enter the source code, a list-window where the entire source code could be browsed, a command/debug-window where instructions were entered that were immediately executed, and the output-window.
As it came standard with many early STs for several years, it rapidly became the standard BASIC for the ST. If a computer magazine was to publish some code, or if someone was to distribute a BASIC file, then using ST BASIC would maximise the number of people who could run the program.