[Cst-1b] Compiler Construction 1.19 - Static Chain method

[Martin Harper]

I'm not clear (at all) on the difference between the "P" frame pointer, and
the "S" static frame pointer, in the "static chain method" on page 23 of the
main notes. :(
>From my understanding, The P pointer points to the previous stack frame.- the
one that you return to after termination of the function call. The S pointer
points to the stack frame that contains the next level up of the "display".
But surely these two stack frames will always be identical?
Help, pointers, insults welcome...
Martin.