Multiple Stack Frames

            STACK SEGMENT
        -----------------------   high addresses
       |                       |
       |                       |
       |-----------------------|  ---------------
       |                       |
       |---PARMS FROM ASTART---|
       |---RETURN TO ASTART----|    MAIN's  FRAME
       |-ASTART'S BASE POINTER-|
       |                       |
       |-----------------------|  ---------------
       |                       |
       |---PARMS FROM MAIN-----|
       |---RETURN TO MAIN------|    SUB 1 FRAME
       |---MAIN's BASE POINTER-|
       |                       |
       |-----------------------|  ---------------
       |                       |
       |---PARMS FROM SUB 1----|
       |---RETURN TO SUB 1-----|    SUB 2 FRAME
       |---SUB 1 BASE POINTER--|
       |                       |
       |-----------------------|  ---------------
       |                       |
       |---PARMS FROM SUB 2----|
       |---RETURN TO SUB 2-----|
BP --> |---SUB 2 BASE POINTER--|    SUB 3 FRAME
       |                       |
       |-----------------------|  ---------------
       |                       |
SP -->  -----------------------   low addresses