Industrial Engineer · phase 3 of 16 · noun

Program

Top-level user-code organization unit that coordinates control logic and calls routines or function blocks.

The Explain card

Plain English: A program is the top level container for a chunk of the controller's logic. It owns its own tags, holds routines, and gets scheduled by a task.
Example: A bottling controller might have a Filler program, a Capper program and a Conveyors program. Each one lives under a task and calls its own routines.
Why it matters: Splitting the project into programs keeps one machine's tags from colliding with another's and lets you give each part its own scan rate. It is also the unit you export, copy and reuse on the next line.
Hook: The folder the machine is filed under.

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

In a sentence

The Program reads the tank high-level input, runs the pump interlock function block, and writes the motor-start output during each PLC scan.

How it is built

Where it came from

Origin: Greek programma, through Late Latin, from pro, meaning before, and graphein, meaning to write
Entered the language: 1630s
What changed: It moved from a written public notice to an ordered plan, then to instructions executed by a computer or controller.

How it is spelled

Pattern: The final root is spelled -gram, as in diagram and telegram.
Pattern: The final m is doubled in programmed, programmer, and programming.
Breaks the pattern: British English commonly uses programme for schedules and plans, but program for computer and controller code.

Spelled like

Broken into chunks

What it sits beside

Same subject

Same shape

IEC 61131-3 program organization 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.