Originally SuperBASIC was intended as the BASIC interpreter for a home computer code-named SuperSpectrum, then under development.
This project was later cancelled; however, SuperBASIC was subsequently included in the ROM firmware of the Sinclair QL microcomputer (announced in January 1984), also serving as the command line interpreter for the QL's QDOS operating system.
[1][2] It was one of the first second-generation BASICs to be integrated into a microcomputer's operating system (unlike BBC BASIC which preceded it in 1981), making the OS user-extendable—as done by Linus Torvalds in his formative years.
Until cleared (e.g. by entering NEW), the function Iso[3] will act like an extension to the operating system.
Similarly, according to the QL User Guide, "many of the operating system commands are themselves defined as procedures.