Professional Assembly Language

Chapter 11. Using Functions

After you start coding various types of utilities for different projects, you will realize that you are coding the same utilities multiple times within the same program, or possibly using the same utilities within different programs. Instead of having to retype the code for the utility every time you need to use it, you can create a standalone function that can be called anytime you need the utility.

This chapter describes what functions are and how they are used in programs. You will learn how functions are used in assembly language, including examples of how they are created and used in assembly language programs. After that, you will learn how to create assembly language functions using the C calling convention, as well as how to split assembly language functions into files separate from the main program. Finally, because passing parameters is important to functions as well as programs, you will learn how to read and process command-line parameters from within an assembly language program, and examine a demonstration of how to use command-line parameters in your application.

Defining Functions

Often, applications require that the same procedures or processes be performed multiple times with different data sets. When the same code is required throughout an application, instead of rewriting the code multiple times, it is sometimes best to create a single function containing the code, which can then be called from anywhere in the program. A function contains ...