Glossary Updates12 new terms added to the glossaries · October 2, 2026, 22:44 CEST
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Glossary · Automation software engineering and architecture

Concurrency

Also known as: Concurrent execution

German: Nebenläufigkeit

In software engineering, concurrency is the property of a system in which several tasks, threads or processes are in progress during overlapping time periods, either interleaved on one processor or running in parallel on several cores, and may share resources or data.

  • Software engineering

In one sentence

Concurrency means several tasks or threads are in progress during overlapping periods and may share resources or data.

Example

A controller runs a 1 ms motion task, a 10 ms logic task and a background communication task concurrently, all accessing shared axis data.

How it applies

  • Engineering: Controllers commonly run several cyclic and event tasks with different priorities, and multicore controllers can run them truly in parallel. Shared data between tasks needs protection, or values can become inconsistent.
  • Risks: Concurrency introduces defects that are hard to reproduce: race conditions, Deadlock, Livelock and priority inversion. They often appear only under specific timing, for example at high load or after a hardware change.
  • Documentation: Document the task model: which tasks exist, their priorities, cycle times, watchdogs and which data they share. This information is essential for developers extending the program and for service engineers analyzing timing problems.

Concurrency vs. parallelism

Concurrency means tasks overlap in time; parallelism means they actually execute at the same instant on different processors. A single-core controller can be concurrent without being parallel. Parallel execution makes some concurrency defects more likely, because interleavings that were rare become common.

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

Source: AI TechDoc Knowledge editorial definition, based on concurrent and real-time programming practice

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 Knowledge and are not part of any standard.

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