The Netwide Assembler (NASM) is an assembler and

disassembler A disassembler is a computer program that translates machine language into assembly language—the inverse operation to that of an assembler. The output of disassembly is typically formatted for human-readability rather than for input to an asse ...

for the

Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California, and Delaware General Corporation Law, incorporated in Delaware. Intel designs, manufactures, and sells computer compo ...

x86 x86 (also known as 80x86 or the 8086 family) is a family of complex instruction set computer (CISC) instruction set architectures initially developed by Intel, based on the 8086 microprocessor and its 8-bit-external-bus variant, the 8088. Th ...

architecture. It can be used to write

16-bit 16-bit microcomputers are microcomputers that use 16-bit microprocessors. A 16-bit register can store 216 different values. The range of integer values that can be stored in 16 bits depends on the integer representation used. With the two ...

32-bit In computer architecture, 32-bit computing refers to computer systems with a processor, memory, and other major system components that operate on data in a maximum of 32- bit units. Compared to smaller bit widths, 32-bit computers can perform la ...

(

IA-32 IA-32 (short for "Intel Architecture, 32-bit", commonly called ''i386'') is the 32-bit version of the x86 instruction set architecture, designed by Intel and first implemented in the i386, 80386 microprocessor in 1985. IA-32 is the first incarn ...

) and

64-bit In computer architecture, 64-bit integers, memory addresses, or other data units are those that are 64 bits wide. Also, 64-bit central processing units (CPU) and arithmetic logic units (ALU) are those that are based on processor registers, a ...

(

x86-64 x86-64 (also known as x64, x86_64, AMD64, and Intel 64) is a 64-bit extension of the x86 instruction set architecture, instruction set. It was announced in 1999 and first available in the AMD Opteron family in 2003. It introduces two new ope ...

) programs. It is considered one of the most popular assemblers for

Linux Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...

and x86 chips. It was originally written by

Simon Tatham Simon Tatham (born 3 May 1977) is a British computer programmer. He created and maintains PuTTY, a free software implementation of Secure Shell (SSH) and Telnet for Microsoft Windows and Unix, along with an xterm terminal emulator. He is also ...

with assistance from Julian Hall. , it is maintained by a small team led by H. Peter Anvin. It is

open-source software Open-source software (OSS) is Software, computer software that is released under a Open-source license, license in which the copyright holder grants users the rights to use, study, change, and Software distribution, distribute the software an ...

released under the terms of a simplified (2-clause)

BSD license BSD licenses are a family of permissive free software licenses, imposing minimal restrictions on the use and distribution of covered software. This is in contrast to copyleft licenses, which have share-alike requirements. The original BSD lic ...

Features

NASM can output several binary formats, including

COFF The Common Object File Format (COFF) is a format for executable, object code, and shared library computer files used on Unix systems. It was introduced in Unix System V, replaced the previously used a.out format, and formed the basis for ext ...

, OMF, a.out,

Executable and Linkable Format In computing, the Executable and Linkable FormatTool Interface Standard (TIS) Portable Formats SpecificationVersion 1.1'' (October 1993) (ELF, formerly named Extensible Linking Format) is a common standard file format for executable files, obje ...

(ELF), Mach-O and

binary file A binary file is a computer file that is not a text file. The term "binary file" is often used as a term meaning "non-text file". Many binary file formats contain parts that can be interpreted as text; for example, some computer document files ...

(.bin, binary disk image, used to compile

operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

s), though

position-independent code In computing, position-independent code (PIC) or position-independent executable (PIE) is a body of machine code that executes properly regardless of its memory address. PIC is commonly used for shared libraries, so that the same library code c ...

is supported only for ELF

object file An object file is a file that contains machine code or bytecode, as well as other data and metadata, generated by a compiler or assembler from source code during the compilation or assembly process. The machine code that is generated is kno ...

s. It also has its own binary format called RDOFF. The variety of output formats allows retargeting programs to virtually any x86 operating system (OS). It can also create flat binary files, usable to write boot loaders,

read-only memory Read-only memory (ROM) is a type of non-volatile memory used in computers and other electronic devices. Data stored in ROM cannot be electronically modified after the manufacture of the memory device. Read-only memory is useful for storing sof ...

(ROM) images, and in various facets of OS development. It can run on non-x86 platforms as a cross assembler, such as

PowerPC PowerPC (with the backronym Performance Optimization With Enhanced RISC – Performance Computing, sometimes abbreviated as PPC) is a reduced instruction set computer (RISC) instruction set architecture (ISA) created by the 1991 Apple Inc., App ...

and SPARC, though it cannot generate programs usable by those machines. NASM uses a variant of Intel assembly syntax instead of AT&T syntax. It also avoids features such as automatic generation of segment overrides (and the related ASSUME directive) used by MASM and compatible assemblers.

Development

NASM version 0.90 was released in October 1996. Version 2.00 was released on 28 November 2007, adding support for

extensions. The development versions are not uploaded to SourceForge.net, but are checked into

GitHub GitHub () is a Proprietary software, proprietary developer platform that allows developers to create, store, manage, and share their code. It uses Git to provide distributed version control and GitHub itself provides access control, bug trackin ...

with binary snapshots available from the project web page. In July 2009, as of version 2.07, NASM was released under the Simplified (2-clause) BSD license. Previously, because it was licensed under

LGPL The GNU Lesser General Public License (LGPL) is a free-software license published by the Free Software Foundation (FSF). The license allows developers and companies to use and integrate a software component released under the LGPL into their own ...

, it led to development of Yasm, a complete rewrite of under the New BSD License. Yasm offered support for x86-64 earlier than NASM. It also added support for

GNU Assembler The GNU Assembler, commonly known as gas or as, is the assembler developed by the GNU Project. It is the default back-end of GCC. It is used to assemble the GNU operating system and the Linux kernel, and various other software. It is a part o ...

syntax.

RDOFF

Relocatable Dynamic Object File Format (RDOFF) is used by developers to test the integrity of NASM's object file output abilities. It is based heavily on the internal structure of NASM, essentially consisting of a header containing a

serialization In computing, serialization (or serialisation, also referred to as pickling in Python (programming language), Python) is the process of translating a data structure or object (computer science), object state into a format that can be stored (e. ...

of the output driver function calls followed by an array of sections containing executable code or data. Tools for using the format, including a linker and loader, are included in the NASM distribution. Until version 0.90 was released in October 1996, NASM supported output of only flat-format executable files (e.g.,

DOS DOS (, ) is a family of disk-based operating systems for IBM PC compatible computers. The DOS family primarily consists of IBM PC DOS and a rebranded version, Microsoft's MS-DOS, both of which were introduced in 1981. Later compatible syste ...

COM file A COM file is a type of simple executable file. On the Digital Equipment Corporation (DEC) VAX operating systems of the 1970s, .COM was used as a filename extension for text files containing commands to be issued to the operating system (sim ...

s). In version 0.90,

added support for an object-file output interface, and for DOS .OBJ files for 16-bit code only. NASM thus lacked a 32-bit object format. To address this lack, and as an exercise to learn the object-file interface, developer Julian Hall put together the first version of RDOFF, which was released in NASM version 0.91. Since this initial version, there has been one major update to the RDOFF format, which added a record-length indicator on each header record, allowing programs to skip over records whose format they do not recognise, and support for multiple segments; RDOFF1 only supported three segments: ''text'', ''data'' and ''bss'' (containing uninitialized data). The RDOFF format is strongly deprecated and has been disabled starting in NASM 2.15.04.

References

External links

* *
Special edition for Win32 and BeOS.

A comparison of GAS and NASM
at

IBM International Business Machines Corporation (using the trademark IBM), nicknamed Big Blue, is an American Multinational corporation, multinational technology company headquartered in Armonk, New York, and present in over 175 countries. It is ...

* : a converter between the source format of the assemblers NASM and

GAS Gas is a state of matter that has neither a fixed volume nor a fixed shape and is a compressible fluid. A ''pure gas'' is made up of individual atoms (e.g. a noble gas like neon) or molecules of either a single type of atom ( elements such as ...

{{X86 assembly topics 1996 software Assemblers Disassemblers DOS software Free and open source compilers Linux programming tools MacOS MacOS programming tools Programming tools for Windows Software using the BSD license

Features

Development

RDOFF

See also

References

Further reading

External links