ISO 4342:1985

Overview

ISO 4342:1985 - "Numerical control of machines - NC processor input - Basic part program reference language" defines a higher‑level, symbolic reference language (RL) for writing part programs that are processed by a computer to produce NC (numerical control) machine programs. Developed primarily for CNC machine tools, the standard specifies language structure, semantics and conventions for creating processor input that a postprocessor converts into machine‑specific CLDATA (cutter location data). Annexes provide practical representation rules and formal syntax: Annex A (punched‑card format), Annex B (syntax description), Annex C (recommended synonyms) and Annex D (word/location index).

Key topics and technical requirements

• Language scope and purpose: A problem‑oriented, symbolic part‑programming language similar to scientific programming languages but tailored to machining and NC programming.
• Processor / postprocessor model: Two‑stage processing - a processor handles the RL and a postprocessor generates machine‑specific NC output (CLDATA). ISO 3592 is cited as the primary reference for CLDATA.
• Coordinate system: Right‑handed Cartesian system with reference axes X, Y, Z related to the workpiece; angles expressed in degrees and decimals; cutter reference point conventions are defined.
• Data types and arithmetic: Entities are numeric (real values with integer and fractional parts) or symbolic; RL supports arithmetic operators, functions and expressions. The standard clarifies semantics (e.g., no implicit type associations).
• Language elements: Definition of letters, digits, special characters, literal strings, identifiers, labels, statements, nesting (including the facility to define entities using parentheses), and part program structure.
• Geometrical and motion statements: Extensive logical pages cover geometrical definitions (points, lines, circles, planes, surfaces, matrices, etc.), motion and toolpath control, tool orientation, and related execution statements.
• Implementation guidance: Annex B provides a formal syntax to assist implementers; Annex A gives representation rules for legacy media (punched cards).

Applications and users

ISO 4342 is useful for:

• CNC programmers and CAM developers creating higher‑level part programs or processor input.
• Postprocessor and NC software vendors implementing CLDATA generation consistent with the RL.
• Machine tool manufacturers and integrators standardizing processor interfaces and toolpath semantics.
• Automation engineers and systems integrators concerned with interoperability between workshop‑level systems and NC controls. Because the RL is a reference language, organizations typically implement subsets or modules to match specific machine capabilities.

Related standards

• ISO 3592 (CLDATA / processor output)
• ISO 841 (coordinate system nomenclature)
• ISO 4343 (processor output minor elements)
• ISO 646 (character set)

Keywords: ISO 4342:1985, numerical control, NC processor input, reference language, part program, CLDATA, CNC programming, postprocessor, language syntax.