Editing FASM

{{short description|Open source assembler for x86 processors}}
{{For|the Royal Navy project also known as "FASM"|Future Attack Submarine}}
{{Infobox software
| name = FASM
| screenshot = FASM2.png
| caption = Screenshot with supplied example
| developer = Tomasz Grysztar
| released = {{Start date and age|2000|03}}
| latest release version = {{wikidata|property|reference|edit|P348}}
| latest release date = {{Start date and age|{{wikidata|qualifier|P348|P577}}}}
| latest_preview_version = 
| latest_preview_date = 
| programming language = Assembly
| operating_system = [[Unix-like]], [[Linux]], [[Microsoft Windows|Windows]] and IDE, [[MS-DOS]] and IDE, [[OpenBSD]], etc., [[MenuetOS]], [[KolibriOS]], [http://octavio.vega.fernandez.googlepages.com/octaos/ OctaOS], DexOS and IDE, [[SkyOS]], [http://www.oby.ro/os/ Solar_OS]
| platform = [[x86]], [[x86-64]]
| genre = [[Assembly language assembler|Assembler]]
| license = [[Simplified BSD license|Simplified BSD]] with a [[weak copyleft]] clause
| website = {{url|flatassembler.net}}
}}

'''FASM''' (''flat assembler'') is an [[assembly language assembler|assembler]] for [[x86]] processors. It supports [[x86 assembly language|Intel-style]] [[assembly language]] on the [[IA-32]] and [[x86-64]] computer architectures. It claims high speed, size optimizations, [[operating system]] (OS) portability, and [[macro (computer science)|macro]] abilities.<ref name="Manual">{{cite web |author=Grysztar |first=Tomasz |date=2008-05-12 |title=Flat Assembler Programmer's Manual |url=http://flatassembler.net/docs.php?article=manual |accessdate=2008-05-12 |website=flat assembler}}</ref><ref name="WhichAsm"/> It is a [[low-level programming language|low-level]] assembler<ref name="WhichAsm"/> and intentionally uses very few [[command line interface|command-line]] options. It is [[free and open-source software]].

All versions of FASM can directly output any of the following: flat "raw" [[binary file|binary]] (usable also as MS-DOS [[COM file|COM executable]] or SYS driver), objects: [[Executable and Linkable Format]] (ELF) or [[COFF|Common Object File Format]] (COFF) (classic or MS-specific), or executables in either [[DOS MZ executable|MZ]], ELF, or [[Portable Executable]] (PE) format (including WDM drivers, allows custom MZ DOS stub). An unofficial port targeting the [[ARM architecture]] ([http://arm.flatassembler.net FASMARM]) also exists.<ref name="ARM">{{cite web|url=http://arm.flatassembler.net/|title=FASMARM|date= 2008-03-20|accessdate=2008-05-12}}</ref>

== History ==
The project was started in 1999 by Tomasz Grysztar, a.k.a. ''Privalov'', at that time an undergraduate student of mathematics from [[Poland]]. It was released publicly in March 2000.<ref name="Interview">{{cite web|url=http://www.wasm.ru/article.php?article=privalov_en|title=Interview with Privalov the author of FASM|date=2004-08-12|access-date=2008-05-12|archive-url=https://web.archive.org/web/20071008021423/http://wasm.ru/article.php?article=privalov_en|archive-date=2007-10-08|url-status=dead}}</ref><ref name="Release">{{cite web |author=Grysztar |first=Tomasz |date=2000-03-15 |title=flat assembler |url=http://marc.info/?l=freedos-dev&m=95311018003959&w=2 |accessdate=2008-05-19}}</ref> FASM is completely written in [[assembly language]] and comes with full source.  It is [[Self-hosting (compilers)|self-hosting]] and has been able to assemble itself since version 0.90 (May 4, 1999).

FASM originally ran in 16-bit [[unreal mode|flat real mode]]. 32-bit support was added and then supplemented with optional [[DOS Protected Mode Interface|DPMI]] support. Designed to be easy to port to any operating system with flat 32-bit addressing, it was ported to Windows, then Linux.

== Design ==
FASM does not support as many [[high-level assembler|high-level]] statements as [[MASM]] or [[TASM]].<ref name="WhichAsm">{{cite web |author=Hyde |first=Randall |title=Which Assembler is the Best? |url=http://mmcs.sfedu.ru/~ulysses/Edu/MP/WhichAsm.html |archive-url=https://archive.today/20131116172530/http://mmcs.sfedu.ru/~ulysses/Edu/MP/WhichAsm.html |url-status=dead |archive-date=November 16, 2013 |accessdate=2008-05-18 }}</ref> It provides syntax features and macros, which make it possible to customize or create missing statements.<ref name="Interview"/> Its memory-addressing syntax is similar to TASM's ideal mode and [[Netwide Assembler|NASM]].  Brackets are used to denote memory operands as in both assemblers, but their size is placed outside the brackets, like in NASM.<ref name="Design"/>

FASM is a multi-pass assembler. It makes extensive code-size optimization and allows unconstrained forward referencing.<ref name="WhichAsm"/><ref name="Design">{{cite web |author=Grysztar |first=Tomasz |title=Flat Assembler Design Principles |url=http://flatassembler.net/docs.php?article=design |accessdate=2008-05-12}}</ref>  An unusual FASM construct is defining procedures only if they are used somewhere in the code, something that in most languages is done per-object by the [[linker (computing)|linker]].

FASM is based on the "same source, same output" principle: the contents of the resulting file are not affected by the command line.<ref name="Design"/> Such an approach saves FASM sources from compiling problems often present in many assembly projects. On the other hand, it makes it harder to maintain a project that consists of multiple separately compiled source files or mixed-language projects. However, there exists a Win32 [[wrapper library|wrapper]] called FA, which mitigates this problem.<ref name="FA">{{cite web |author=Grysztar |first=Tomasz |title=FA – command line extension for fasm |url=http://board.flatassembler.net/topic.php?t=9948 |accessdate=2012-05-11}}</ref> FASM projects can be built from one source file directly into an executable file without a linking stage.<ref name="WhichAsm" />

== IDE ==
'''Fresh''', an internet community supported project started by John Found, is an [[integrated development environment]] for FASM.<ref name="fresh">{{cite web |last=Found |first=John |title=Fresh ID project |url=https://fresh.flatassembler.net/}}</ref>   Fresh currently supports Microsoft Windows and Linux.<ref name=fresh/>

== Use ==
Operating systems written with FASM:
* [[MenuetOS]]<ref name="MenuetOS">{{cite web|url=http://www.menuetos.net/|title=MenuetOS|accessdate=2008-05-18}}</ref> – 32- and [[64-bit]] GUI operating systems by Ville Turijanmaa
* [[KolibriOS]]

Compilers that use FASM as a backend:
* [[PureBasic]]
* [[High Level Assembly]] (HLA)
* [[BlitzMax]]

== See also ==
* [[Comparison of assemblers]]

== References ==
{{Reflist}}

== External links ==
* FASM project: {{official website|flatassembler.net}}
* [http://fasmlib.x86asm.net/ FASMLIB] 0.8.0 – portable 32-bit x86 asm lib for FASM/MASM/YASM/NASM/GASM
* [http://arm.flatassembler.net FASMARM] – FASM for ARM processors, <small> v1.27, {{Release date|2012|06|09}}</small>
* [http://fresh.flatassembler.net/ The Fresh IDE]

{{X86 assembly topics}}

[[Category:2000 software]]
[[Category:Assemblers]]
[[Category:DOS software]]
[[Category:Free software primarily written in assembly language]]
[[Category:Linux programming tools]]
[[Category:Programming tools for Windows]]
[[Category:Self-hosting software]]
[[Category:Unix programming tools]]