# Programming a custom POU

1. Prerequisite
2. You must create a custom Program Organisation Unit before you can program it.

1. Start editing the real-time application.
2. In the menu bar, click Program.
3. Select the custom POU from the POU tree.
4. Create local variables in the context of the custom POU.
5. Change the data type and initial value as required.
6. Change the section of all variables that serve as inputs to VAR_INPUT.
7. Change the section of all variables that serve as outputs to VAR_OUTPUT.
8. Add the local variables to the custom POU.
9. Add POUs from the catalogue to the custom POU.
10. Connect the elements in the worksheet as required.

Creating a local variable

Adding a variable to a program

Adding a POU to a program

Data types

Functions and function blocks of the standard library