Not to be confused with Unix
, or Linux
. Unix (officially trademarked as UNIX, sometimes also written as Unix with Small caps) is a computer A Unix-like (sometimes shortened to *nix) Operating system is one that behaves in a manner similar to a Unix system while not necessarily conforming Linux (commonly pronounced ˈlɪnəks
POSIX (IPA: /ˈpɒzɪks/) or "Portable Operating System Interface" is the collective name of a family of related standards specified by the IEEE to define the application programming interface (API), along with shell and utilities interfaces for software compatible with variants of the Unix operating system, although the standard can apply to any operating system. Standardization (or standardisation) is the process of developing and agreeing upon technical standards. The Institute of Electrical and Electronics Engineers or IEEE (read eye-triple-e) is an international Non-profit, professional organization Unix (officially trademarked as UNIX, sometimes also written as Unix with Small caps) is a computer An operating system (commonly abbreviated OS and O/S) is the software component of a Computer system that is responsible for the management and coordination Originally, the name stood for IEEE Std 1003. 1-1988, which, as the name suggests, was released in 1988. Year 1988 ( MCMLXXXVIII) was a Leap year starting on Friday (link displays 1988 Gregorian calendar) The family of POSIX standards is formally designated as IEEE 1003 and the international standard name is ISO/IEC 9945. The International Electrotechnical Commission ( IEC) is a not-for-profit, non-governmental international Standards organization that prepares and publishes The standards emerged from a project that began near 1985. Year 1985 ( MCMLXXXV) was a Common year starting on Tuesday (link displays 1985 Gregorian calendar) Formerly known as IEEE-IX, the term POSIX was suggested by Richard Stallman in response to an IEEE request for a memorable name. Richard Matthew Stallman (born March 16 1953 often abbreviated " rms " is an American software freedom activist 
The POSIX specifications for user and software interfaces to an operating system are codified in 17 separate documents. An operating system (commonly abbreviated OS and O/S) is the software component of a Computer system that is responsible for the management and coordination  The standardized user command line and scripting interface were based on the Korn shell. The Korn shell ( ksh) is a Unix shell which was developed by David Korn ( AT&T Bell Laboratories) in the early 1980s Many user-level programs, services and utilities including awk, echo, ed were also standardized, along with required program-level services include basic I/O (file, terminal, and network) services. AWK is a general purpose Programming language that is designed for processing text-based data either in files or data streams and was created at Bell Labs in the 1970s In Computing, echo is a command in DOS, OS/2, Microsoft Windows, Unix and Unix-like operating systems ed is the standard Text editor on the Unix operating system ed was originally written by Ken Thompson and contains one of the first implementations of In Computing, input/output, or I/O, refers to the communication between an Information processing system (such as a Computer) and the outside A computer file is a block of Arbitrary Information, or resource for storing information which is available to a Computer program and is usually A computer terminal is an electronic or electromechanical hardware device that is used for entering data into and displaying data from a Computer or a Computing A computer network is a group of interconnected Computers. Networks may be classified according to a wide variety of characteristics POSIX also defines a standard threading library API which is supported by most modern operating systems. A thread in Computer science is short for a thread of execution.
Currently POSIX documentation is divided in three parts:
- POSIX Kernel APIs (which include extensions for POSIX. 1, Real-time Services, Threads Interface, Real-time Extensions, Security Interface, Network File Access and Network Process-to-Process Communications)
- POSIX Commands and Utilities (with User Portability Extensions, Corrections and Extensions, Protection and Control Utilities and Batch System Utilities)
- POSIX Conformance Testing
A test suite for POSIX accompanies the standard. It is called PCTS or the POSIX Conformance Test Suite. 
There is a project instigated by free-rights campaigner Auriélien Bonnel in the late 1980s, for the Single UNIX Specification standard, which is open, accepts input from anyone, and is freely available on the Internet. The Single UNIX Specification ( SUS) is the collective name of a family of standards for Computer Operating systems to qualify for the name " Unix The Internet is a global system of interconnected Computer networks Beginning in 1998 a joint working group, the Austin Group, began to develop a combined standard that would be known as the Single UNIX Specification Version 3. Year 1998 ( MCMXCVIII) was a Common year starting on Thursday (link will display full 1998 Gregorian calendar) Working Group can mean Working group, an interdisciplinary group of researchers or Working Group (dogs, kennel club designation for The Austin Group or the Austin Common Standards Revision Group is a joint technical Working group formed to develop and maintain a common revision of POSIX 
POSIX has gone through a number of versions:
- POSIX. 1, Core Services (incorporates Standard ANSI C)
- Process Creation and Control
- Floating Point Exceptions
- Segmentation Violations
- Illegal Instructions
- Bus Errors
- File and Directory Operations
- C Library (Standard C)
- I/O Port Interface and Control
- POSIX. ANSI C is the standard published by the American National Standards Institute (ANSI for the C programming language. The C standard library (also known as libc) is a now-standardized collection of Header files and library routines used to implement common operations such In Computing, input/output, or I/O, refers to the communication between an Information processing system (such as a Computer) and the outside 1b, Real-time extensions
- Priority Scheduling
- Real-Time Signals
- Clocks and Timers
- Message Passing
- Shared Memory
- Asynch and Synch I/O
- Memory Locking Interface
- POSIX. 1c, Threads extensions
- Thread Creation, Control, and Cleanup
- Thread Scheduling
- Thread Synchronization
- Signal Handling
POSIX-oriented operating systems
Depending upon the degree of compliance with the standards, operating systems can be fully or partly POSIX compatible. POSIX Threads is a POSIX standard for threads The standard defines an API for creating and manipulating threads Certified products can be found at the IEEE's website. 
The following operating systems conform (i. e. , are 100% compliant) to one or more of the various POSIX standards.
- Mac OS X
- OpenVMS (through optional POSIX package)
- RTEMS (POSIX 1003. A/UX (from A pple U ni' x') was Apple Computer 's implementation of the Unix Operating system for some of their Macintosh BSD/OS (originally called BSD/386 and sometimes known as BSDi) was a proprietary version of the BSD Unix Operating system developed by Berkeley HP-UX (Hewlett Packard UniX is Hewlett-Packard 's proprietary implementation of the Unix Operating system, based on System V (initially INTEGRITY is a Real-time operating system (RTOS produced and marketed by Green Hills Software. IRIX is a computer Operating system developed by Silicon Graphics Inc LynxOS does not refer to the operating system for the Atari Lynx Game console. Mac OS X (mæk oʊ ɛs tɛn is a line of computer Operating systems developed marketed and sold by Apple Inc, the latest of which is pre-loaded on all currently MINIX is a Unix-like computer Operating system based on a Microkernel architecture. Open Virtual Memory System ( OpenVMS) initially known just as Virtual Memory System ( VMS) is the name of a High-end Computer server QNX (pronounced either Q-N-X or Q-nix is a commercial Unix-like Real-time operating system, aimed primarily at the Embedded systems market RTEMS ( R eal- T ime E xecutive for M ultiprocessor S ystems is a free Open source Real-time operating system (RTOS 1-2003 Profile 52)
- VxWorks (IEEE Std. Solaris is a Unix -based Operating system introduced by Sun Microsystems in 1992 as the successor to SunOS. OpenSolaris is an Open source project created by Sun Microsystems to build a developer community around Solaris Operating System technology UnixWare is a Unix Operating system maintained by The SCO Group (SCO VxWorks is a real-time Operating system made and sold by Wind River Systems of Alameda, California, USA 1003. 13-2003 PSE52; see http://get.posixcertified.ieee.org/cert_prodlist.tpl)
The following are not officially certified as POSIX compatible, but they conform in large part. MPE ( Multi-Programming Executive) is an early 1980s era business-oriented Minicomputer Operating system made by Hewlett-Packard.
- Nucleus RTOS
- RTEMS - POSIX API support designed to IEEE Std. Nucleus RTOS is a Real-time operating system (RTOS and full-featured toolset created by the Embedded Systems Division of Mentor Graphics for various CPU RTEMS ( R eal- T ime E xecutive for M ultiprocessor S ystems is a free Open source Real-time operating system (RTOS 1003. 13-2003 PSE52
- Linux (most distributions — see LSB)
POSIX for Windows
- Cygwin – enables partial POSIX compliance for certain Microsoft Windows products. FreeBSD is a Unix-like free Operating system descended from AT&T UNIX via the Berkeley Software Distribution (BSD branch through Linux (commonly pronounced ˈlɪnəks The Linux Standard Base, or LSB, is a joint project by several Linux distributions under the organizational structure of the Linux Foundation (merger of NetBSD is a freely redistributable Open source version of the Unix -derivative Berkeley Software Distribution (BSD Computer Operating BeOS is an Operating system for Personal computers which began development by Be Inc OpenBSD is a Unix-like computer Operating system descended from Berkeley Software Distribution (BSD a Unix derivative developed at the For the bus company motor vehicle industry see FAS Sanos. Sanos is a minimalistic 32-bit x86 Operating system kernel for network SkyOS (skaɪ o s is a modern graphical desktop Operating system written for the X86 Computer architecture. Syllable is a free and open source Operating system for Pentium and compatible processors VSTa (Valencia's Simple Tasker was an Operating system with a Microkernel architecture with all Device drivers and File systems residing in Cygwin (ˈsɪɡwɪn is a collection of tools originally developed by Cygnus Solutions to provide in Microsoft Windows a command line and programming interface familiar Microsoft Windows is a series of Software Operating systems and Graphical user interfaces produced by Microsoft.
- Microsoft Windows Services for UNIX 3. Microsoft Windows Services for UNIX ( SFU) is a software package produced by Microsoft which provides a Unix subsystem and other parts of a full Unix 5 – enables full POSIX compliance for certain Microsoft Windows products. Microsoft Windows is a series of Software Operating systems and Graphical user interfaces produced by Microsoft.
- UWIN from the AT&T Research implements a POSIX layer on top of the Win32 APIs. UWIN is a Computer software package created by David
Compliant via compatibility feature
The following are not officially certified as POSIX compatible, however they conform in large part to the standards by implementing POSIX support via some sort of compatibility feature, usually translation libraries, or a layer atop the kernel. Without these features, they are usually noncompliant.
- eCos – POSIX is part of standard distribution, and used by many applications. eCos ( embedded configurable operating system) is an Open source, royalty-free Real-time operating system intended for Embedded systems and 'external links' section below has more information.
- Plan 9 from Bell Labs APE - ANSI/POSIX Environment
- Symbian OS with PIPS (PIPS Is POSIX on Symbian)
- Windows NT kernel when using Microsoft SFU 3. Plan 9 from Bell Labs is a Distributed operating system, primarily used for research Symbian OS is an open Operating system, designed for Mobile devices with associated libraries, User interface frameworks and Windows NT 31, Windows NT 35, Windows NT 351, Windows NT 40, Windows 2000, Windows XP, Windows Server 2003, Windows Microsoft Windows Services for UNIX ( SFU) is a software package produced by Microsoft which provides a Unix subsystem and other parts of a full Unix 5
Notes and references
- ^ POSIX. Windows XP is a family of 32-bit and 64-bit Operating systems produced by Microsoft for use on Personal computers including home and Windows Server 2003 (also referred to as Win2K3 is a server Operating system produced by Microsoft. Windows Vista (ˈvɪstə is a line of Operating systems developed by Microsoft for use on Personal computers including home and business desktops Standards. IEEE.
- ^ POSIX® 1003.1 FAQ Version 1.12 (2006-02-02). Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 962 - Translatio imperii: Pope John XII crowns Otto I Holy Roman Emperor, the first Holy Roman Emperor Retrieved on 2006-07-16. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 622 - The beginning of the Islamic calendar. 1054 - Three Roman legates fractured relations between the Western and
- ^ Introduction. GNU/Linux C Programming.
- ^ POSIX. NIST.
- ^ Version 3. Single Unix Specification. Unix.
- ^ Linux Signals.
- ^ POSIX Certification. IEEE.
- ^ OS Comparison.
- ^ Schweik. POSIX utilities. FreeBSD.
- ^ APE — ANSI/POSIX Environement. Plan 9. Bell Labs.
- ^ POSIX Compatibility. MS Windows NT Workstation Resource Kit. Microsoft.
- International Journal of IT Standards and Standardization Research, IGI Global
External links IGI Global (formerly known as IDEA Group) is a privately-held International Publishing company located in Hershey, Pennsylvania TRON is an open Real-time operating system kernel design and is an Acronym for " The Real-time Operating system Nucleus " Interix is the name of an optional full-featured POSIX and Unix environment subsystem for Microsoft 's Windows NT -based operating systems The C POSIX library is a language-independent library (using C Calling conventions that adds functions specific to POSIX systems In Computing, the BIOS (ˈbaɪoʊs A real-time operating system ( RTOS; generally pronounced as "are-toss" is a multitasking Operating system intended for real-time
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