Beta BASIC, by Betasoft, was an extended BASIC for Sinclair ZX Spectrum microcomputer.
Beta BASIC was upwards compatible with Spectrums ROM basic. It added many new commands and enhancements, such as procedures, DO LOOPs, dynamic arrays, windows, multiple font sizes, and even KEYIN command that allowed a running program to modify itself. In addition it contained many toolkit functions and an improved editor.
The latest version, 3.0, was published in the year 1985.
SAM BASIC for SAM Coupé microcomputer was based on Beta BASIC.