Software - Forth

Forth resources (not all of these are specific to the 6502, but can still be useful for reference):

Forth books:

• Starting Forth is a classic introductory Forth book
• Thinking Forth is a classic intermediate/advanced Forth book
• Programming a Problem-Oriented Language is a book written by Chuck Moore (inventor of Forth) in 1970, though unpublished at the time.

Forth standards:

• The Forth-79 spec (text version)
• The Forth-83 spec (html)
• The 1994 ANS spec (text version)
• The 2012 ANS spec

FIG-Forth

• Forth Interest Group
• Taygeta archive
• FIG-Forth
• FIG-Forth Installation Guide
• 6502 Forth assembler by William F. Ragsdale (OCR copy, so there are some errors such as the letter O which should be the digit 0 and lowercase l which should be the digit 1), originally published in Forth Dimensions, volume 3 number 5 pp. 143-150 (pp. 11-18 of the .pdf); the code is on pp. 149-150 (pp. 17-18 of the .pdf); note that this assembler is in the public domain, see p. 134 (p. 2 of the .pdf)
• FIG-Forth 86 screens; the Fig-Forth 8086 implementation (can be extracted with 7-Zip; note that the .DOC files are text, not a Microsoft Word document). Many (though not all) of the screens are also applicable to the 6502.

Non-6502 Forth implementations:

• eForth is a forth that is designed for easy of porting; there are only about 30 primitives and the rest of the system is written in high level Forth (consequently, eForth is relatively slow for a Forth implementation).
• gForth is a full featured ANS Forth, with a lot of high level Forth code.
• third (buzzard2 at the link) is a Forth variant (it was a IOCCC 1992 winner); like eForth, it has a small number of primitives (13) and the rest of the language is bootstrapped from there. Spoiler link for those who don't want to decipher the various obfuscations.