Programs
The controller operating system is a preemptive multitasking system that is in compliance with IEC 61131-3. This system provides the following:
- Programs to group data and logic
- Routines to encapsulate executable code that is written in one programming language
Each program contains the following:
- Local Tags
- Parameters
- A main executable routine
- Other routines
- An optional fault routine
Program Within a Control Application
Programs the Controller Organizer and Logical Organizer

Scheduled and Unscheduled Programs
The scheduled programs within a task execute to completion from first to last. Programs that are not attached to any task show up as unscheduled programs.
Unscheduled programs within a task are downloaded to the controller with the entire project. The controller verifies unscheduled programs but does not execute them.
You must schedule a program within a task before the controller can scan the program. To schedule an unscheduled program, use the Program/Phase Schedule tab of the Task Properties dialog box.
Schedule an Unscheduled Program

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