Command Key Usage:

Specify how the panel design connects with other panel designs. This can be done in two different ways:

For each command key on a panel design, specify an action to be taken if the command key is pressed; the action may be expressed either as the name of another panel design to be displayed, or as a keyword denoting a standard function:
- *PRV: display previous panel.
- *SAME: re-display panel.
- *EXIT: exit program.
- *EXEC: execute a command string, specified in the text field.
Specify an action to be taken conditional on a value being entered for a particular line and column on the panel design. For instance, on a subfile display, specify that a 5 entered against a selection field on a line will cause a separate display of details for that line to be displayed.

The branching information has a number of uses:

It can appear as part of the documentation for the panel design.
It will be used by the interactive Display Panel Design utility (YDSPPNL) to simulate the program’s action if a command key is pressed, or an option selected.
It provides programmers with an exact description of a designer’s intentions regarding program flow.