The flat assembler is a fast and efficient self-assembling x86 assembler for DOS, Windows and Linux operating systems. Currently it supports x86 and x86-64 instructions sets with MMX, 3DNow!, SSE up to SSE4, AVX, AVX2 and XOP extensions, can produce output in plain binary, MZ, PE, COFF or ELF format. It includes the powerful but easy to use macroinstruction support and does multiple passes to optimize the instruction codes for size. The flat assembler is self-compilable and the complete source code is included. The only difference between the various flat assembler packages is the operating system on which they can be executed. From given source each version will generate exactly the same output file, so with each of the following releases you can compile programs for any operating system. Site: http://flatassembler.net