Run time structures

each variable and parameter needs memory space during execution

memory space is organised per procedure

activation frame for each procedure invocation:

Run time Stack

activation frames maintained for all active procedures

stack means last in, first out

Procedure call and return

procedure call:

• save program counter on top of stack
• add activation frame for called procedure to stack
• initialise in and in out parameters using actuals
• set program counter to start of called procedure

procedure return:

• return out and in out values to actuals
• dispose of activation frame for finished procedure
• retrieve program counter from stack