Assembly Language Questions Medium
In Assembly Language, subroutines are implemented using the concept of a subroutine call and return mechanism.
When a subroutine is called, the program execution jumps to the starting address of the subroutine code. This is achieved by using a specific instruction, such as CALL or JSR, which saves the return address (the address of the instruction following the subroutine call) onto the stack or in a designated register.
Once inside the subroutine, the required operations are performed, and any necessary parameters can be passed to the subroutine through registers or the stack. The subroutine can also modify the values of registers or memory locations as needed.
After the subroutine completes its execution, it uses a specific instruction, such as RET or RTS, to return control back to the calling program. This instruction retrieves the saved return address from the stack or register and jumps to that address, continuing the execution of the calling program from where it left off.
Subroutines allow for modular programming, as they can be reused in different parts of the program. They also help in organizing code and improving code readability and maintainability. Additionally, subroutines can be nested, meaning one subroutine can call another subroutine, and the return addresses are saved accordingly.
Overall, subroutines in Assembly Language provide a structured way to break down complex tasks into smaller, manageable units, enhancing code reusability and maintainability.