The stacking PC linkage and the basic PC linkage provide the following capabilities:

• The PC routine's PKM authority can be increased.
• Basic PC routines must receive control in primary mode; stacking PC routines have the option to do so.
• Basic PC routines must receive control with SASN=old PASN; stacking PC routines have the option to do so.
• The PC routine can receive control in either problem state or supervisor state.
• The PC routine can be either a space switch routine or a non-space switch routine.

The stacking PC linkage also provides the following additional capabilities that the basic PC linkage does not provide:

• The PC routine's PKM authority can be decreased.
• The PC routine's PSW key can be set from data in the entry table.
• The PC routine can receive control in AR mode.
• An entry point to an associated recovery routine (ARR) can be defined in the entry table.
• The system automatically uses the linkage stack to save and restore the user's environment.