Writing ARM and Thumb Assembly Language
2-12 Copyright © 2000, 2001 ARM Limited. A ll rights reserved. ARM DUI 0068B
2.3 Structure of assembly language modules
Assembly language is the language that the ARM assembler (
armasm
) parses and
assembles to produce object code. This can be:
•ARM assembly language
•Thumb assembly language
•a mixture of both.
2.3.1 Layout of assembly language source files
The general form of source lines in assembly language is:
{label} {instruction|directive|pseudo-instruction} {;comment}
Note
Instructions, pseudo-instructions, and directives must be preceded by white space, such
as a space or a tab, even if there is no lab el.
All three sections of the source line are optional. You can use blank lines to make your
code more readable.
Case rules
Instruction mnemonics, directives, and symbolic register names can be written in
uppercase or lowercase, but not mixed.
Line length
To make source files easier to read, a long line of source can be split onto several lines
by placing a backslash character ( \ ) at the end of the line. The backslash must not be
followed by any other characters (including spaces and tabs). The backslash/end-of-line
sequence is treated by the assembler as wh ite space.
Note
Do not use the backslash/end-of-line sequence within quoted strings.
The exact limit on the length of lines, including any extensions using backslashes,
depends on the contents of the line, but is generally between 128 and 255 characters.