Glossary Updates12 new terms added to the glossaries · October 2, 2026, 22:44 CEST
AI TechDocKnowledge

Glossary · PLC and control programming

Software quality

Also known as: Software product quality

German: Softwarequalität

In software engineering, software quality is the degree to which software meets stated requirements and user needs, described in ISO/IEC 25010 by characteristics such as functional suitability, performance efficiency, compatibility, reliability, security and maintainability.

  • PLC programming
  • Standards

In one sentence

Software quality is the degree to which software meets requirements and needs, measured by traits such as reliability and security.

Example

A PLC library is released only after static code analysis, a review against the coding guideline and unit tests with 90 percent branch coverage.

How it applies

  • Engineering: Quality in PLC software shows in readable structure, consistent naming, tested reusable blocks and predictable timing. Static analysis tools, coding guidelines (for example from PLCopen) and reviews make it measurable.
  • Testing: Test coverage figures show how much of the code tests exercise; they do not prove that requirements are met. Verification checks the software against its specification; Validation checks that it serves its intended use.
  • Maintenance: Maintainability is often the quality characteristic with the largest long-term cost impact, because machines run for decades and are changed many times.
  • Documentation: Software documentation is part of quality: a program nobody can understand is hard to maintain safely. Define in the quality plan which documents a software release requires.

Software quality vs. functional safety

High software quality is a precondition for safety but not the same thing. Functional safety standards add specific requirements, techniques and evidence for safety-related software.

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

Source: AI TechDoc Knowledge editorial definition, based on ISO/IEC 25010, Systems and software Quality Requirements and Evaluation (SQuaRE)

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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