Explain how the jsr and rts instructions are involved with s

Explain how the jsr and rts instructions are involved with subroutines. Specifically, explain how

the stack pointer is involved with all this

Solution

A subroutine is a section of code which performs a specific task,
usually a task which needs to be executed by different parts of the program
Its a specialized program module that may be called upon many times during the
course of execution of program
Like,mathematical functions, such as square root (sqrt)
Because a subroutine can be called from different places in a program, you cannot get
out of a subroutine with an instruction such as jmp label
because you would need to jump to different places depending upon which section of
the code called the subroutine.

Stack applications are to store return addresses during subroutine executions .
When one wants to call the subroutine, the code has to save the addres where the
subroutine should return to. It does this by saving the return address on the stack.
Its to control the transfer of data into or ourt of computer uses an externally generated signal
called interrupt.
This is done automatically for you when you get to the subroutine by
using JSR (Jump to Subroutine)instruction. This instruction pushes the address of the
instruction. All subroutines must end with either the instruction RTS(return from subroutine)
or RTR(return and restore condition stores)following the JSR instruction on the stack
After the subroutine is done executing its code, it needs to return to the address saved
on the stack.This is done automatically when you return from the subroutine by
using RTS (Return from Subroutine) instruction. This instruction pulls
the return address off the stack and loads it into the PC.