BASIC

BASIC was a very popular language for microcomputers in the early 1980s. I wrote several BASIC interpreters, the last two being BASIC 5.1 and BASIC 6.0.

BASIC 5.1

BASIC 5.1 was a full-featured BASIC interpreter for the Z80. It featured 64-bit BCD floating-point arithmetic, string processing, graphics, and disk I/O. BASIC 5.1 also included modern programming language constructs not traditionally associated with BASIC: block-structured IF-THEN-ELSE-ENDIF, WHILE-WEND, REPEAT-UNTIL, and symbolic labels. It was easy to program in BASIC 5.1 without the use of GOTO. The language had 98 reserved words.

BASIC 5.1 could run the over 100 BASIC programs that I had developed for it and earlier versions.

BASIC 6.0

BASIC 6.0 was the integer counterpart to BASIC 5.1. BASIC 6.0 replaced the 64-bit BCD floating-point with 16-bit binary integers to gain a factor of two increase in speed on programs that required only integers. BASIC 6.0 was otherwise the same language and shared much of the same source code.