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.
