Subroutines
A subroutine is a section of code which can be invoked repeatedly as the program executes.
Reason for Use
- Save effort in programming.
- Reduce the size of programs.
- Share code.
- Encapsulate or package a specific activity.
- Provide easy access to tried and tested code.
Subroutines in Assembly
Before we answer the above questions, let us look at how subroutines can be declared ans used in assembly language.
The declaration of a simple procedure looks as follows:
label PROC
...
RET ;return
label ENDP
The subroutine is initiated by writing CALL label.
PROC and ENDP are not part of the Intel x86 instruction set. We must call a C library functions from the inline assembler.