Glossary Updates12 new terms added to the glossaries · October 2, 2026, 22:44 CEST
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Glossary · PLC and control programming

Soft PLC

Also known as: Software PLC, Virtual PLC, Runtime PLC

German: Soft-SPS

In industrial automation, a soft PLC is PLC runtime software that executes IEC 61131-3 or comparable control programs on general-purpose computing hardware, such as an industrial PC, often with a real-time operating system or real-time extension.

  • PLC programming

In one sentence

A soft PLC is PLC runtime software that runs control programs on general-purpose hardware such as an industrial PC.

Example

A machine builder runs its PLC logic as a soft PLC on an industrial PC that also hosts the HMI and a vision application.

How it applies

  • Engineering: Soft PLCs allow control, HMI, motion and data processing on one computer. Real-time behavior depends on the runtime design, operating system configuration and hardware; it must be verified for the specific system.
  • Operation: The PC underneath needs the same care as any IT system: operating system updates, antivirus policy, user rights and backups, coordinated with the real-time requirements. See Patch management.
  • Virtualization: Soft PLCs are the basis for virtual PLCs running in containers or on edge servers, one element of Software-defined automation. Latency and determinism over the network are then critical design questions.
  • Documentation: Document the hardware, operating system version, runtime version and configuration that were validated. Updates of any layer can change behavior and need a controlled process.

Soft PLC vs. hardware PLC

A hardware PLC combines dedicated hardware and firmware from one vendor. A soft PLC separates runtime software from hardware. The programming languages are the same; the responsibilities for hardware, operating system and updates differ.

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

Source: AI TechDoc Blog editorial definition, based on PC-based control 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 Blog and are not part of any standard.

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