Forth 2012 Standard

1 Introduction

1.1 Purpose

The purpose of this standard is to promote the portability of Forth programs for use on a wide variety of computing systems, to facilitate the communication of programs, programming techniques, and ideas among Forth programmers, and to serve as a basis for the future evolution of the Forth language.

1.2 Scope

This standard specifies an interface between a Forth System and a Forth Program by defining the words provided by a Standard System.

1.2.1 Inclusions

This standard specifies:
  • the forms that a program written in the Forth language may take;
  • the rules for interpreting the meaning of a program and its data.

1.2.2 Exclusions

This standard does not specify:

  • the mechanism by which programs are transformed for use on computing systems;
  • the operations required for setup and control of the use of programs on computing systems;
  • the method of transcription of programs or their input or output data to or from a storage medium;
  • the program and Forth system behavior when the rules of this standard fail to establish an interpretation;
  • the size or complexity of a program and its data that will exceed the capacity of any specific computing system or the capability of a particular Forth system;
  • the physical properties of input/output records, files, and units;
  • the physical properties and implementation of storage.

1.3 Document organization

1.3.1 Word sets

This standard groups Forth words and capabilities into word sets under a name indicating some shared aspect, typically their common functional area. Each word set may have an extension, containing words that offer additional functionality. These words are not required in an implementation of the word set.

The "Core" word set, defined in sections 1 through 6, contains the required words and capabilities of a Standard System. The other word sets, defined in sections 7 through 18, are optional, making it possible to provide Standard Systems with tailored levels of functionality.

1.3.1.1 Text sections

Within each word set, section 1 contains introductory and explanatory material and section 2 introduces terms and notation used throughout the standard. There are no requirements in these sections.

Sections 3 and 4 contain the usage and documentation requirements, respectively, for Standard Systems and Programs, while section 5 specifies their labeling.

Sections x.1–x.6 of each word set have the same section numbering as sections 1–6 of the whole document to make it easy to relate the sections to each other. This may lead to gaps in section numbers if a particular section does not occur in a word set.

1.3.1.2 Glossary sections

Section 6 of each word set specifies the required behavior of the definitions in the word set and the extensions word set.

1.3.2 Annexes

The annexes do not contain any required material.

Annex A provides some of the rationale behind the committee's decisions in creating this standard, as well as implementation examples. It has the same section numbering as the body of the standard to make it easy to relate each requirements section to its rationale section.

Annex B is a short bibliography on Forth.

Annex C discusses the compatibility of this standard with earlier Forths.

Annex D presents some techniques for writing portable programs.

Annex H is an index of all Forth words defined in this standard.

1.4 Future directions

1.4.1 New technology

This standard adopts certain words and practices that are increasingly found in common practice. New words have also been adopted to ease creation of portable programs.

1.4.2 Obsolescent features

This standard adopts certain words and practices that cause some previously used words and practices to become obsolescent. Although retained here because of their widespread use, their use in new implementations or new programs is discouraged, as they may be withdrawn from future revisions of the standard.

This standard designates the following word as obsolescent:

15.6.2.1580 FORGET
6.2.2530[COMPILE]
13.6.2.1795 LOCALS|

This standard designates the following practice as obsolescent:

  • Using ENVIRONMENT? to enquire whether a word set is present.

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