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

Modal command

Also known as: Modal function, Modal code

German: Modaler Befehl

In CNC programming, a modal command is a function or value that stays in effect after the block in which it is programmed until it is canceled or replaced by another command of the same group.

  • CNC
  • Standards

In one sentence

A modal command stays in effect in a CNC program until it is canceled or replaced, for example G01 or a programmed feed rate.

Example

After G01 F200 in block N10, the following blocks move linearly at 200 mm/min without repeating G01 or F until G00 is programmed.

How it applies

  • Programming: Interpolation mode, plane selection, unit system, feed rate and the active Work offset are typically modal. Programmers must know the active modal state at every block, especially after a program restart in the middle of a program.
  • Operation: Many controls show the active modal G-codes on the screen. When a program is restarted at a block, the control or the operator has to restore the correct modal state first.
  • Documentation: Programming guidelines should list which commands are modal on the specific control and recommend a safe start block that sets all relevant modal states explicitly. This is a typical content for a reference topic in the machine's programming manual.

Modal vs. nonmodal command

A Nonmodal command acts only in the block where it is written, such as a dwell. A modal command changes the control's state; its effect is best understood with a State model: the command is a transition, the active mode is the state.

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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