Memory Stack

Stack could exist as a stand-alone unit or could be executed in a random-access memory attached to the CPU. The implementation of a stack in a CPU is done by assigning portion of memory. A portion of memory is assigned to the stack operation and the processor register is used as a stack pointer to execute stack in CPU. Figure below represent a portion of computer memory partitioned into three segments -program, data and stack. The address of next instruction in program is located by program counter PC while an array of data is pointed by an address register AR. The top of stack is located by stack pointer SP. The three registers are connected to the common address bus that connects three registers and either one can provide the address for memory. PC is used during fetch phase to read an instruction. AR is used during execute phase to read an operand. SP is used to push or pop items into or from stack.