Static Allocation .

. callee.static-area and callee.code-area are constants referring to address of the activation record and the first address of called procedure respectively.

. #here+20 in the move instruction is the return address; the address of the instruction following the goto instruction

. A return from procedure callee is implemented by

GOTO *callee.static-area

For the call statement, we need to save the return address somewhere and then jump to the location of the callee function. And to return from a function, we have to access the return address as stored by its caller, and then jump to it. So for call, we first say: MOV #here+20, callee.static-area. Here, #here refers to the location of the current MOV instruction, and callee.static- area is a fixed location in memory. 20 is added to #here here, as the code corresponding to the call instruction takes 20 bytes (at 4 bytes for each parameter: 4*3 for this instruction, and 8 for the next). Then we say GOTO callee.code-area, to take us to the code of the callee, as callee.codearea is merely the address where the code of the callee starts. Then a return from the callee is implemented by: GOTO *callee.static area. Note that this works only because callee.static-area is a constant.