The Portable Operating System Interface is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines application programming interfaces (APIs), along with command line shells and utility interfaces, for software compatibility (portability) with variants of Unix and other operating systems. POSIX is also a trademark of the IEEE. POSIX is intended to be used by both application and system developers.
The Single UNIX Specification (SUS) is a standard for computer operating systems, compliance with which is required to qualify for using the "UNIX" trademark. The standard specifies programming interfaces for the C language, a command-line shell, and user commands. The core specifications of the SUS known as Base Specifications are developed and maintained by the Austin Group, which is a joint working group of IEEE, ISO/IEC JTC 1/SC 22/WG 15 and The Open Group. If an operating system is submitted to The Open Group for certification, and passes conformance tests, then it is deemed to be compliant with a UNIX standard such as UNIX 98 or UNIX 03.
In computing, endianness is the order in which bytes within a word of digital data are transmitted over a data communication medium or addressed in computer memory, counting only byte significance compared to earliness. Endianness is primarily expressed as big-endian (BE) or little-endian (LE), terms introduced by Danny Cohen into computer science for data ordering in an Internet Experiment Note published in 1980. The adjective endian has its origin in the writings of 18th century Anglo-Irish writer Jonathan Swift. In the 1726 novel Gulliver's Travels, he portrays the conflict between sects of Lilliputians divided into those breaking the shell of a boiled egg from the big end or from the little end. By analogy, a CPU may read a digital word big end first, or little end first.
The Netwide Assembler (NASM) is an assembler and disassembler for the Intel x86 architecture. It can be used to write 16-bit, 32-bit (IA-32) and 64-bit (x86-64) programs. It is considered one of the most popular assemblers for Linux and x86 chips.
The Portable Executable (PE) format is a file format for executables, object code, dynamic-link-libraries (DLLs), and binary files used on 32-bit and 64-bit Windows operating systems, as well as in UEFI environments. It is the standard format for executables on Windows NT-based systems, including files such as .exe, .dll, .sys, and .mui. At its core, the PE format is a structured data container that gives the Windows operating system loader eveything it needs to properly manage the executable code it contains. This includes references for dynamically linked libraries, tables for importing and exporting APIs, resource management data and thread-local storage (TLS) information.
In computing, a system call is the programmatic way in which a computer program requests a service from the operating system on which it is executed. This may include hardware-related services, creation and execution of new processes, and communication with integral kernel services such as process scheduling. System calls provide an essential interface between a process and the operating system.
The GNU C Library, commonly known as glibc, is the GNU Project implementation of the C standard library. It provides a wrapper around the system calls of the Linux kernel and other kernels for application use. Despite its name, it now also directly supports C++. It was started in the 1980s by the Free Software Foundation (FSF) for the GNU operating system.
Large-file support (LFS) is the term frequently applied to the ability to create files larger than either 2 or 4 GiB on 32-bit filesystems.
In software engineering, a compatibility layer is an interface that allows binaries for a legacy or foreign system to run on a host system. This translates system calls for the foreign system into native system calls for the host system. With some libraries for the foreign system, this will often be sufficient to run foreign binaries on the host system. A hardware compatibility layer consists of tools that allow hardware emulation.
A fat binary is a computer executable program or library which has been expanded with code native to multiple instruction sets which can consequently be run on multiple processor types. This results in a file larger than a normal one-architecture binary file, thus the name.
Unix System V is one of the first commercial versions of the Unix operating system. It was originally developed by AT&T and first released in 1983. Four major versions of System V were released, numbered 1, 2, 3, and 4. System V Release 4 (SVR4) was commercially the most successful version, being the result of an effort, marketed as Unix System Unification, which solicited the collaboration of the major Unix vendors. It was the source of several common commercial Unix features. System V is sometimes abbreviated to SysV.
The history of Unix dates back to the mid-1960s, when the Massachusetts Institute of Technology, Bell Labs, and General Electric were jointly developing an experimental time-sharing operating system called Multics for the GE-645 mainframe. Multics introduced many innovations, but also had many problems. Bell Labs, frustrated by the size and complexity of Multics but not its aims, slowly pulled out of the project. Their last researchers to leave Multics – among them Ken Thompson, Dennis Ritchie, Doug McIlroy, and Joe Ossanna – decided to redo the work, but on a much smaller scale.
The GUID Partition Table (GPT) is a standard for the layout of partition tables of a physical computer storage device, such as a hard disk drive or solid-state drive, using universally unique identifiers (UUIDs), which are also known as globally unique identifiers (GUIDs). Forming a part of the Unified Extensible Firmware Interface (UEFI) standard, it is nevertheless also used for some BIOSs, because of the limitations of master boot record (MBR) partition tables, which use 32 bits for logical block addressing (LBA) of traditional 512-byte disk sectors.
a.out is a file format used in older versions of Unix-like computer operating systems for executables, object code, and, in later systems, shared libraries. This is an abbreviated form of "assembler output", the filename of the output of Ken Thompson's PDP-7 assembler. The term was subsequently applied to the format of the resulting file to contrast with other formats for object code.
In computing, a dynamic linker is the part of an operating system that loads and links the shared libraries needed by an executable when it is executed, by copying the content of libraries from persistent storage to RAM, filling jump tables and relocating pointers. The specific operating system and executable format determine how the dynamic linker functions and how it is implemented.
The GNU Binary Utilities, or binutils, is a collection of programming tools maintained by the GNU Project for working with executable code including assembly, linking and many other development operations.
This is a comparison of binary executable file formats which, once loaded by a suitable executable loader, can be directly executed by the CPU rather than being interpreted by software. In addition to the binary application code, the executables may contain headers and tables with relocation and fixup information as well as various kinds of meta data. Among those formats listed, the ones in most common use are PE, ELF, Mach-O and MZ.
Unix is a family of multitasking, multi-user computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and others. Initially intended for use inside the Bell System, AT&T licensed Unix to outside parties in the late 1970s, leading to a variety of both academic and commercial Unix variants from vendors including University of California, Berkeley (BSD), Microsoft (Xenix), Sun Microsystems (SunOS/Solaris), HP/HPE (HP-UX), and IBM (AIX).
ptrace is a system call found in Unix and several Unix-like operating systems. By using ptrace one process can control another, enabling the controller to inspect and manipulate the internal state of its target. ptrace is used by debuggers and other code-analysis tools, mostly as aids to software development.
crypt is a POSIX C library function. It is typically used to compute the hash of user account passwords. The function outputs a text string which also encodes the salt, and identifies the hash algorithm used. This output string forms a password record, which is usually stored in a text file.
