Figure 1 shows how the stacking PC and the BAKR instructions add entries to TCBA's linkage stack and how the PR instruction removes those entries.

The program call from Program 1 to Program 2 automatically places all the caller's status on the linkage stack (adding Entry 1 to the linkage stack). Program 2 uses the BALR instruction to branch to a subroutine, which uses the BAKR instruction to save Program 2's status (adding Entry 2 to the stack). When the subroutine returns to Program 2 through the PR instruction, Program 2's status is restored (removing Entry 2 from the stack). When Program 2 uses the PR instruction to return to Program 1, Program 1's status is restored (removing Entry 1 from the stack). At any time, the entry formed by the most recent BAKR or stacking PC instruction contains the status of the caller of the currently executing code.

Figure 1. Example of using the linkage stack