NASM

The Netwide Assembler (NASM) is a popular assembler for the x86/x64 architecture. NASM is open source software and is freely available from their official website.

NASM is available for many operating systems, including (but not limited to) Windows, GNU/Linux, BSD and Solaris. Because it is Open Source, NASM can be made to run on pretty much any operating system, and is a common choice for a first port to a hobby OS.

Comparison to GAS

Those preferring it over gas claim its easy syntax and powerful macro capabilities are a plus. On the other hand, other users claim gas is better integrated into the GNU Compiler Collection (GCC) and has more cross-platform capabilities. Similar to editor and browser discussions, this is likely to remain an unresolved debate.

Tips

• Use -w+orphan-labels. Often, labels without colons were not really intended to be labels, and are actually misspellings or typos. This flag will cause NASM to warn you if there are labels without colons. On newer versions, this warning is enabled by default.
• Explicitly define your sections. While NASM defaults to .text, it doesn't put labels declared as globals in .text correctly, unless the label is preceded by a section directive at some point.
• Use the -g flag to generate debug information. For ELF files it uses DWARF by default. Other debugging formats can be selected with the -F flag.

See also

• Critique of NASM from a TASM user

Articles

• Tool Comparison
• GAS
• Assembly

External Links

• NASM home page
• NASM manual
• PC Assembly Book Introduction to x86 assembly using NASM
• Assembly Language Step-by-Step: Programming with Linux, a book about learning Assembly language using NASM
• The NASMX project (formerly NASM32) is a collection of macros, include files and examples that are meant to accelerate NASM programming; including helpers to begin developing 32-bit and 64-bit Windows, Linux and XBox applications.