The flat assembler (abbreviated to fasm) is a fast self-assembling
assembler for DOS, Windows
and Linux operating systems. It was designed primarily for the assembly of x86 instructions and it supports x86 and x86-64 instructions sets with MMX, 3DNow!, SSE up to SSE4, AVX, AVX2, XOP and AVX-512 extensions and 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 size of instruction codes.
The flat assembler is self-hosting 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.
Although flat assembler is freeware, donations are greately appreciated to help cover cost and time-loss.
It is a great help in maintaining this project.
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Apart from the command line version for Windows console this package contains the one with integrated syntax-highlighting editor,
so you can edit, compile and execute your programs from one place. It also contains the set of includes
with equates and macroinstructions for Windows programming and some examples of Windows programs created with
help of them. The provided documentation is in PDF format.
This version can be executed from command line of any operating system compatible with DOS and contains
few tiny examples of DOS programs. It also contains the documentation in text format using DOS character set.
If you want to use flat assembler from the command line of Windows system, you should use the Windows console version instead of this one.
This is version for all platforms that have support for the ELF object format and the C library, like OpenBSD or Zeta.
The object file provided in this package can be linked with the 32-bit C library to create the final executable
for any such system. The documentation in pure ASCII format is included.
The flat assembler g (abbreviated to fasmg) is a new assembly engine
designed to become a successor of the one used by flat assembler 1.
It does not have a built-in support for x86 instructions. It is a generic assembler that can be used in place of flat assembler 1 in
applications where only the pure macroinstruction engine is needed instead of x86 encoder, for example when an instruction set for a different architecture is defined through macroinstructions. However it still has the ability of self-hosting, thanks to the included set of macroinstructions implementing basic x86 instructions and formats.
This release contains executables for 32-bit Linux and Windows, plus an experimental executable for MacOS. It is packaged with examples of macroinstructions that allow assembly of simple programs for the architectures like x86, x64, 8052, AVR, or Java Virtual Machine.
The following are some third-party products based on flat assembler, they are available to download from their respective websites.