Industrial Engineer · phase 3 of 16 · noun

Routine / Function

Reusable or callable unit of logic that performs a defined operation.

The Explain card

Plain English: A routine is a named piece of logic inside a program, and a function is a callable piece of logic that returns a result. Both exist so you can name a job and call it instead of repeating it.
Example: A Main routine calls an Alarms routine, a Motors routine and a Sequence routine in order every scan. A scaling function is called with raw counts and hands back engineering units.
Why it matters: A routine that is never called never runs, which is the first thing to check when new logic seems dead. Functions keep no memory between calls, so anything that needs to remember goes in a function block instead.
Hook: Name the job once and call it by name.

How the word is built, where it came from, and what it sits beside in memory.

In a sentence

The PLC calls the Routine each scan to scale the analog pressure input before alarm comparison.

How it is built

Where it came from

Origin: French routine, formed from route, meaning road or course, and the suffix -ine
Entered the language: 1670s
What changed: It moved from a traveled course to an established procedure, then acquired its programming sense in the 20th century.

How it is spelled

Pattern: The letters ou represent the /uː/ sound.
Pattern: The final ine represents the stressed /iːn/ sound common in French-derived words.

Spelled like

Broken into chunks

What it sits beside

Same subject

Same shape

IEC 61131-3 program organization units

callable logic units

Phase 3: PLC Program Organization and Execution

How the logic is arranged and how the scan actually runs it, which is the difference between code that works and code that works every time.