Masterminds of Programming

Chapter 4. Forth

Forth is a stack-based, concatenative language designed by Chuck Moore in the 1960s. Its main features are the use of a stack to hold data, and words that operate on the stack, popping arguments and pushing results. The language itself is small enough that it runs on anything from embedded machines to supercomputers, and expressive enough to build useful programs out of a few hundred words. Successors include Chuck Moore’s own colorForth, as well as the Factor programming language.

The Forth Language and Language Design

How do you define Forth?

Chuck Moore: Forth is a computer language with minimal syntax. It features an explicit parameter stack that permits efficient subroutine calls. This leads to postfix expressions (operators follow their arguments) and encourages a highly factored style of programming with many short routines sharing parameters on the stack.

I read that the name Forth stands for fourth-generation software. Would you like to tell us more about it?

Chuck: Forth is derived from “fourth,” which alludes to "fourth-generation computer language.” As I recall, I skipped a generation. FORTRAN/COBOL were first-generation languages; Algol/Lisp, second. These languages all emphasized syntax. The more elaborate the syntax, the more error checking is possible. Yet most errors occur in the syntax. I determined to minimize syntax in favor of semantics. And indeed, Forth words are loaded with meaning.

You consider Forth a language toolkit. I can understand ...