Introduction to Forth

  1. What is Forth?
    Forth is a programming language invented by Chuck Moore around 1970. He called it Forth because he thought of it as a fourth generation language.
  2. What does that mean?
    A fourth generation language is a high level programming language. A high level language is easy for a programmer to code in, as the commands and syntax are like speaking a natural language (like English). Where once a programmer had to type 0s and 1s to add two numbers together, now just typing 3 + 5 will do.
  3. If it is like speaking a natural language, why is it spelled wrong?
    The machine Chuck was working on back in 1970 only allowed file names to have five characters, so the 'u' was left out. For a long time, it was written as 'FORTH' because Chuck's machine didn't have lower case letters either, but since it isn't an acronym, today it is written as 'Forth.'
  4. So in Forth I can add numbers together?
    Yes. But you can do much more.
  5. Such as ... ?
    A Forth program is made up of "words." To Forth, a word is the name for an operation that Forth can perform (e.g. the word to print spaces to the screen is ... SPACES). To Forth, a word can be any sequence of letters or symbols, so "+", "-", and "*" are all considered "words" by Forth. Just like natural languages, Forth stores all the words it knows about in a "dictionary." Over time, you can add new words to Forth's dictionary by defining the new words in terms of the old words (e.g. a "Giant" is a "Large Man").

    Forth provides words to:

    In short, Forth does everything that other programming languages do.

    You do two things with words in a Forth program:

  6. That sounds complicated. Is Forth difficult to learn?
    Compared to what? As Forth is not derived from any other programming languages, the Forth ANSI standard recommends that a new Forth programmer "invest some time mastering its large command repertoire. After a month or so of full time use ..."
  7. I don't have a month! I just want to see what this can do!
    Oh so you want to program?
    Well ...
    Since you've made it this far, why don't you launch Misty Beach Forth? It contains an embedded tutorial hidden under the Help menu.

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Last Updated: 24-June-2001
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