Node:Review - elements of a Forth system, Next:Where to go next, Previous:Forth is written in Forth, Up:Introduction

Review - elements of a Forth system

To summarise this chapter:

• Forth programs use factoring to break a problem down into small fragments called words or definitions.
• Forth program development is an interactive process.
• The main command loop that accepts input, and controls both interpretation and compilation, is called the text interpreter (also known as the outer interpreter).
• Forth has a very simple syntax, consisting of words and numbers separated by spaces or carriage-return characters. Any additional syntax is imposed by parsing words.
• Forth uses a stack to pass parameters between words. As a result, it uses postfix notation.
• To use a word that has previously been defined, the text interpreter searches for the word in the name dictionary.
• Words have interpretation semantics and compilation semantics.
• The text interpreter uses the value of state to select between the use of the interpretation semantics and the compilation semantics of a word that it encounters.
• The relationship between the interpretation semantics and compilation semantics for a word depend upon the way in which the word was defined (for example, whether it is an immediate word).
• Forth definitions can be implemented in Forth (called high-level definitions) or in some other way (usually a lower-level language and as a result often called low-level definitions, code definitions or primitives).
• Many Forth systems are implemented mainly in Forth.