Closed-loop-system
A closed-loop system is a system that continuously monitors its output and adjusts its behavior using feedback to achieve the desired result.
“A system in which the controlling action or input is dependent on the output or changes in output.”
(Definition reproduced from the ISTQB Glossary. Copyright belongs to ISTQB.)
View the complete ISTQB GlossaryWhat is Closed-loop-system?
Unlike open-loop systems, closed-loop systems automatically respond to changes by comparing actual results with expected values and making corrections.
Feedback mechanism: Output influences future system behavior.
Automatic adjustment: The system reacts to changing conditions.
Testing considerations: Verify correct responses under varying feedback conditions.
Real World Example
A regulated product team is preparing a release where Closed-loop-system appears in reviews, test design conversations, or defect triage rather than as an isolated glossary word.
The risk is that the team treats Closed-loop-system as interchangeable with nearby ISTQB terms. That makes test scope blurry and can lead to weak evidence for the release decision.
The tester anchors the discussion in the official definition, asks where the concept appears in the product, and designs examples that show the difference between Closed-loop-system and similar ideas.
The page becomes useful in practice because Closed-loop-system is connected to a specific testing decision, not memorized as a detached definition.
Practice Questions
Question 1
Which observation MOST indicates instability in a closed‑loop system?
Question 2
Which test BEST evaluates autoscaling control?
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