What is Forth?

Forth is a little-used computer programming language, quite different from conventional languages, which is based on a stack and uses inverted polish notation. For example, to write the sum of 4 and 7 you would write  "4 7 + ." (stack 4, stack 7, sum the two elements on the top of the stack, show the result).

Many people consider"Starting forth", by Leo Brodie, the best introduction to Forth.

You can find Forth tutorials in many other places, such as:
http://dec.bmth.ac.uk/forth/forth.html (Forth: an underview)
http://www.zeppe.com/forthtut.html (Forth tutorial)

If you want Forth interpreters or compilers:

• You can find GNU Forth for several operating systems at www.complang.tuwien.ac.at/forth/gforth/ and read more about it at www.jwdt.com/~paysan/gforth.html
• kForth is available at ccreweb.org/software/kforth/kforth.html
• SwiftForth is a commercial product by Forth, Inc
• You can find several more compilers/interpreters (for 8051 microcontrolers, for example) at  www.idiom.com/free-compilers/LANG/Forth-1.html.