Professional Assembly Language

Chapter 4. A Sample Assembly Language Program

With all of your development tools in order, it's time to start learning about assembly language programming. Assembly language programs use a common template and format (specific to the assembler used), which you can develop and use for all of your applications.

This chapter walks you through a basic assembly language program template for the GNU assembler. The first section of the chapter describes the common items found in assembly language programs, and how they can be used to define a common template. The next section shows a sample program, and how to assemble and run it. Next you will learn how to debug the sample program using the GNU debugger. The last section of this chapter demonstrates how to incorporate C library functions into your assembly language programs.

The Parts of a Program

As shown in Chapter 1, "What Is Assembly Language?," the assembly language program consists of defined sections, each of which has a different purpose. The three most commonly used sections are as follows:

• The data section

• The bss section

• The text section

The text section is required in all assembly language programs. It is where the instruction codes are declared within the executable program. The data and bss sections are optional, but often used within a program. The data section declares data elements that are declared with an initial value. These data elements are used as variables within the assembly language program. The bss section declares ...