Editing GNU Assembler (section)

==General syntax==
GAS supports a general syntax that works for all of the supported architectures. The general syntax includes assembler directives and a method for commenting. The default syntax is [[AT&T syntax]].

===Directives===
GAS uses assembler [[directive (programming)|directives]] (also known as pseudo ops), which are keywords beginning with a period that behave similarly to preprocessor directives in the [[C (programming language)|C programming language]]. While most of the available assembler directives are valid regardless of the target architecture, some directives are machine dependent.<ref>{{cite web | title = The GNU Assembler - Assembler Directives | url = http://sources.redhat.com/binutils/docs-2.12/as.info/Pseudo-Ops.html#Pseudo%20Ops | access-date = 2008-04-13 | archive-date = 2012-02-22 | archive-url = https://web.archive.org/web/20120222005603/http://sources.redhat.com/binutils/docs-2.12/as.info/Pseudo-Ops.html#Pseudo%20Ops | url-status = dead }}</ref>

Since version 2.10, Intel syntax can be used through use of the <code>.intel_syntax</code> directive.<ref>{{cite web| title = GNU Assembler News| url = https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f=gas/NEWS;hb=HEAD |quote=A new pseudo-op .intel_syntax has been implemented to allow gas to parse i386 assembly programs with intel syntax.}}</ref><ref>{{cite web| title = AT&T Syntax versus Intel Syntax| url = http://sources.redhat.com/binutils/docs-2.12/as.info/i386-Syntax.html| access-date = 28 July 2014| archive-date = 20 June 2011| archive-url = https://web.archive.org/web/20110620054249/http://sources.redhat.com/binutils/docs-2.12/as.info/i386-Syntax.html| url-status = dead}}</ref><ref>{{cite web| title = Linux assemblers: A comparison of GAS and NASM| author = Ram Narayan| date = 2007-10-17| publisher = IBM DeveloperWorks| url = http://www.ibm.com/developerworks/linux/library/l-gas-nasm.html| archive-url = https://web.archive.org/web/20090303224539/http://ibm.com/developerworks/linux/library/l-gas-nasm.html| archive-date = 3 March 2009| access-date = 28 July 2014}}</ref>

===Comments===
GAS supports two comment styles.<ref>{{cite web|last=Red Hat Inc.|title=Using as|url=http://sources.redhat.com/binutils/docs-2.12/as.info/Comments.html#Comments|access-date=Jan 10, 2013|archive-date=June 20, 2011|archive-url=https://web.archive.org/web/20110620054223/http://sources.redhat.com/binutils/docs-2.12/as.info/Comments.html#Comments|url-status=dead}}</ref>

'''Multi-line'''

As in C, multi-line comments start and end with mirroring slash-asterisk pairs:
<syntaxhighlight lang="c">
/* 
comment
*/
</syntaxhighlight>

'''Single-line'''

Single line comments have a few different formats varying on which architecture is being assembled for.
* A [[hash symbol]] (#) — [[i386]], [[x86-64]], [[i960]], [[68HC11]], [[68HC12]], [[VAX]], [[V850]], [[M32R]], [[PowerPC]], [[MIPS architecture|MIPS]], [[Motorola 68000 series|M680x0]], and [[RISC-V]]
* A [[semicolon]] (;) — [[AMD 29k]] family, [[Advanced RISC Computing|ARC]], [[H8/300]] family, [[PA-RISC|HPPA]], [[PDP-11]], [[picoJava]], Motorola, and [[M32C]]
* The [[at sign]] (@) — 32-bit [[ARM architecture|ARM]]
* A double [[Slash (punctuation)|slash]] (//) — [[AArch64]]
* A [[vertical bar]] (|) — [[Motorola 68000 series|M680x0]]
* An [[exclamation mark]] (!) — [[SuperH|Renesas SH]]