nasm

General-purpose multi-platform x86 and amd64 assembler

The Netwide Assembler (NASM) is an x86 and amd64 (x86-64) assembler designed for portability and modularity. It will output flat-form binary files, a.out (Linux and *BSD), COFF, ELF32, ELF64, Mach-O, Microsoft OMF (OBJ), Win32, Win64, as86 (Minix/Linux bin86 v0.3), LADsoft IEEE-695, Intel hex, Motorola S-record, and a home-grown format called RDOFF. NASM syntax is similar to Intel's, but is less complex. It supports Pentium, P6, MMX, 3DNow!, SSE, SSE2, SSE3, SSE4.1, SSE4.2, XOP/FMA4/CVT16 (rev 3.03), and x64 opcodes, among others. It has strong support for macro conventions. The port also includes NDISASM, a binary file disassembler which uses the same instruction set as NASM.