Acorn System BASIC

Acorn System BASIC and Atom BASIC are two closely related dialects of the BASIC programming language developed by Acorn Computers for their early microcomputers like the Acorn System 3 and Acorn Atom. Developed in-house, they have a number of significant idiosyncrasies compared to most BASIC dialects of the home computer era.

In particular, the language lacked statements for many of the machine's internal functions and provided this using direct access and manipulation of memory locations using indirection operators instead of PEEK and POKE. Both also lacked floating-point support, although this could be added with an optional ROM which introduced further idiosyncrasies. System and Atom BASIC differ primarily in that Atom used the same indirection system to provide rudimentary string manipulation, which Standard lacked, and added a small number of new statements for computer graphics.

Most of these oddities were removed when the underlying system was greatly expanded to produce BBC BASIC on the Atom's successor, the BBC Micro. BBC BASIC ROMs were later offered to Atom users.