Platform(s): TS 1000
Date: 1982
Price: $29.95
Rarity: uncommon

Full implementation of FORTH for the ZX81/TS1000. Runs up to 10 times faster than Basic.

ZX-FORTH complies with the FORTH-79 standard, with the exceptions of replacing the # sign with the British pound symbol, the @ sign with a question mark, the exclamation point with *, an apostrophe with the word “tick”, and “[” and “]” with “(” and “)”. FORTH is unique in its ability to allow the programmer to build program solving modules then assign them user—defined names.

FORTH uses a stack for math, with a last-on/first-off structure, similar to Reverse Polish notation. All arithmetic is integer and may use single or double precision and is faster than ZX/TS BASIC.

Conditional branching is supported and tests usually change the top number on the stack as a flag. ZX-FORTH supports ELSE for second level conditional execution.

User can exit to BASIC and return to ZX-FORTH through a USR call. ZX-FORTH retains all variables, constants, operators and the dictionary.

Though written for cassette storage, ZX-FORTH can be patched to support disks with routines less than 40 bytes long. Cassette load/save is faster than Sinclair BASIC.

ZX-FORTH comes with a 64 page manual that include a bibliography of FORTH references. It has 6K of workspace when used with a 16K RAM pack. The size of the workspace can be increased with more memory.

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