forth

stack-based interactive programming language

TLDR

Start Forth interpreter (Gforth)

$ gforth

Run Forth script

$ gforth [script.fs]

Evaluate expression

$ gforth -e "[1 2 + .] [bye]"

Include file then go interactive

$ gforth [script.fs] -

Forth is a stack-based programming language known for its simplicity and extensibility. Gforth is the GNU implementation of Forth, conforming to the ANS Forth standard.Forth uses reverse Polish notation (RPN) with an explicit stack. Words (functions) are defined with `:` and `;`. The language is highly interactive and extensible, commonly used in embedded systems.

PARAMETERS

-e code

Evaluate Forth code.

-m size

Dictionary size.

-d size

Data stack size.

-r size

Return stack size.

file

Forth source file to load.

Read from stdin.

BASIC OPERATIONS

$ \ Push numbers, add, print
2 3 + .   \ prints 5

\ Define a word
: square ( n -- n^2 ) dup * ;
5 square .   \ prints 25

\ Stack manipulation
1 2 3 swap   \ 1 3 2
dup          \ duplicates top
drop         \ removes top

CAVEATS

Stack-based paradigm differs from most languages. Manual memory management. Limited standard library compared to modern languages. Debugging can be challenging.

HISTORY

Forth was invented by Charles H. Moore in the late 1960s for controlling radio telescopes. It became popular in embedded systems due to its small footprint and efficiency. Gforth was started in 1992 by Anton Ertl and Bernd Paysan.