Glossary Updates12 new terms added to the glossaries · October 2, 2026, 22:44 CEST
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Glossary · CNC and machine tools

Program block (NC)

Also known as: NC block, Block

German: Programmsatz

In CNC programming, a program block is one line of an NC program, made up of words such as the block number, preparatory functions, coordinates, feed rate, spindle speed and miscellaneous functions, which the control processes as a unit.

  • CNC
  • Standards

In one sentence

A program block is one line of an NC program that the control processes as a unit, made up of address words such as N, G, X, F and M.

Example

The block N40 G01 X25.0 Z-10.0 F0.2 moves the tool linearly to the given point at a feed of 0.2 mm per revolution.

How it applies

  • Programming: Each block consists of words: an address letter plus a value. The control reads, interprets and executes blocks one after another; look-ahead functions process several blocks in advance for smooth motion.
  • Testing: In single-block mode the control stops after every block, which is the usual way to check a new program carefully.
  • Documentation: Programming examples should show complete blocks with a short explanation of every word. When a manual explains a block, state which words are modal so readers understand what the next block inherits.

Program block vs. PLC block

In PLC programming, 'block' refers to program organization units such as function blocks or data blocks. A program block in CNC is a line of an NC program. Qualify the term when both worlds meet, for example in documentation for a CNC with an integrated PLC.

By knowledge.aitechdoc.world · Published September 26, 2026 · Last reviewed

Source: ISO 6983-1:2009, Automation systems and integration — Numerical control of machines — Program format and definitions of address words — Part 1: Data format for positioning, line motion and contouring control systems

Definitions follow the cited standards and specifications. Where a source is a copyrighted publication, such as an ISO, IEC or EN standard, the definition is a close paraphrase, not a verbatim quotation, so as not to infringe copyright. We recommend reading the original publication. The sections “How it applies” are editorial commentary by AI TechDoc Blog and are not part of any standard.

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