Editing FASM (section)

== 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" />