4: Program Format
- Page ID
- 19882
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This chapter summarizes the formatting requirements for assembly language programs. The formatting requirements are specific to the yasm assembler. Other assemblers may be slightly different. A complete assembly language program is presented to demonstrate the appropriate program formatting. A properly formatted assembly source file consists of several main parts;
- Data section where initialized data is declared and defined.
- BSS section where uninitialized data is declared.
- Text section where code is placed.
The following sections summarize the basic formatting requirements. Only the basic formatting and assembler syntax are presented. For additional information, refer to the yasm reference manual (as noted in Chapter 1, Introduction).
- 4.1: Comments
- The semicolon (;) is used to note program comments.
- 4.2: Numeric Values
- Number values may be specified in decimal, hex, or octal.
- 4.3: Defining Constants
- Constants are defined with equ.
- 4.4: Data Section
- The initialized data must be declared in the "section .data" section. There must be a space after the word 'section'. All initialized variables and constants are placed in this section. Variable names must start with a letter, followed by letters or numbers, including some special characters (such as the underscore, "_"). Variable definitions must include the name, the data type, and the initial value for the variable.
- 4.5: BSS Section
- Uninitialized data is declared in the "section .bss" section. There must be a space after the word 'section'. All uninitialized variables are declared in this section. Variable names start with a letter followed by letters or numbers including some special characters (such as the underscore, "_"). Variable definitions must include the name, the data type, and the count.
- 4.6: Text Section
- The code is placed in the "section .text" section. There must be a space after the word 'section'. The instructions are specified one per line and each must be a valid instruction with the appropriate required operands. The text section will include some headers or labels that define the initial program entry point.