Evolution of Unix and Unix-like systems, and at and OS family Unix Working state Current Source model Historically, while some Unix projects (including family and ) are Initial release Development started in 1969 First manual published in November 1971 ( 1971-11) Announced outside Bell Labs in October 1973 ( 1973-10) English type Varies;, Default and Varies; some versions are, others are / Official website Unix (; trademarked as UNIX) is a family of, computer that derive from the original Unix, development starting in the 1970s at the research center by, and others. Initially intended for use inside the, AT&T Unix to outside parties in the late 1970s, leading to a variety of both academic and commercial Unix variants from vendors including , , , and. In the early 1990s, AT&T sold its rights in Unix to, which then sold its Unix business to the (SCO) in 1995.

The UNIX trademark passed to, a neutral industry consortium, which allows the use of the mark for certified operating systems that comply with the (SUS). As of 2014, the Unix version with the largest installed base is 's. Unix systems are characterized by a that is sometimes called the '. This concept entails that the operating system provides a set of simple tools that each performs a limited, well-defined function, with a unified (the ) as the main means of communication, and a scripting and command language (the ) to combine the tools to perform complex workflows. Unix distinguishes itself from its predecessors as the first operating system: almost the entire operating system is written in the, thus allowing Unix to reach numerous platforms. The ancestor of all modern Unix systems Unix was originally meant to be a convenient platform for programmers developing software to be run on it and on other systems, rather than for non-programmers.

The system grew larger as the operating system started spreading in academic circles, as users added their own tools to the system and shared them with colleagues. At first, Unix was not designed to be. Later, Unix gradually gained portability, multi-tasking and capabilities in a configuration. Unix systems are characterized by various concepts: the use of for storing data; a hierarchical; treating devices and certain types of (IPC) as files; and the use of a large number of, small programs that can be strung together through a using, as opposed to using a single monolithic program that includes all of the same functionality. These concepts are collectively known as the '.

And summarize this in as 'the idea that the power of a system comes more from the relationships among programs than from the programs themselves'. In an era when a standard computer consisted of a hard disk for storage and a for (I/O), the Unix file model worked quite well, as I/O was generally linear. In the 1980s, and the set of mechanisms were augmented with, and, and were added to support communication with other hosts. As graphical user interfaces developed, the file model proved inadequate to the task of handling asynchronous events such as those generated by a. By the early 1980s, users began seeing Unix as a potential universal operating system, suitable for computers of all sizes. The Unix environment and the program model were essential elements in the development of the and the reshaping of computing as centered in rather than in individual computers.

Both Unix and the were developed by AT&T and distributed to government and academic institutions, which led to both being ported to a wider variety of machine families than any other operating system. Under Unix, the operating system consists of many libraries and utilities along with the master control program, the. The kernel provides services to start and stop programs, handles the and other common 'low-level' tasks that most programs share, and schedules access to avoid conflicts when programs try to access the same resource or device simultaneously.

To mediate such access, the kernel has special rights, reflected in the division between - although in implementations, like or, functions such as network protocols may also run in user space. (sitting) and working together at a The origins of Unix date back to the mid-1960s when the, and were developing, a operating system for the mainframe computer.

Multics featured, but also presented severe problems. Frustrated by the size and complexity of Multics, but not by its goals, individual researchers at Bell Labs started withdrawing from the project.

Unix Operating System Pdf

The last to leave were, and, who decided to reimplement their experiences in a new project of smaller scale. This new operating system was initially without organizational backing, and also without a name. The new operating system was a single-tasking system. In 1970, the group coined the name Unics for Uniplexed Information and Computing Service (pronounced '), as a on Multics, which stood for Multiplexed Information and Computer Services.

Takes credit for the idea, but adds that 'no one can remember' the origin of the final spelling Unix. Dennis Ritchie, Doug McIlroy, and also credit Kernighan. The operating system was originally written in, but in 1973, Version 4 Unix was rewritten in. Version 4 Unix, however, still had many PDP-11 dependent codes, and is not suitable for porting. The first port to other platform was made five years later (1978) for.

Bell Labs produced several versions of Unix that are collectively referred to as '. In 1975, the first source license for UNIX was sold to at the Department of Computer Science. UIUC graduate student Greg Chesson, who had worked on the UNIX kernel at Bell Labs, was instrumental in negotiating the terms of the license. During the late 1970s and early 1980s, the influence of Unix in academic circles led to large-scale adoption of Unix ( and ) by commercial startups, including,. In the late 1980s, AT&T and developed System V Release 4 , which was subsequently adopted by many commercial Unix vendors. In the 1990s, Unix and Unix-like systems grew in popularity as BSD and distributions were developed through collaboration by a worldwide network of programmers. In 2000, Apple released, also a Unix system, which became the core of the Mac OS X operating system, which was later renamed.

Unix operating systems are widely used in modern,. Standards. The (CDE), part of the In the late 1980s, an open operating system standardization effort now known as provided a common baseline for all operating systems; based POSIX around the common structure of the major competing variants of the Unix system, publishing the first POSIX standard in 1988. In the early 1990s, a separate but very similar effort was started by an industry consortium, the (COSE) initiative, which eventually became the (SUS) administered. Starting in 1998, the Open Group and IEEE started the, to provide a common definition of POSIX and the Single UNIX Specification, which, by 2008, had become the Open Group Base Specification. In 1999, in an effort towards compatibility, several Unix system vendors agreed on SVR4's (ELF) as the standard for binary and object code files. The common format allows substantial binary compatibility among Unix systems operating on the same CPU architecture.

The was created to provide a reference directory layout for Unix-like operating systems, and has mainly been used in Linux. Components. This section does not any. Unsourced material may be challenged. (January 2017) The Unix system is composed of several components that were originally packaged together. By including the development environment, libraries, documents and the portable, modifiable source code for all of these components, in addition to the of an operating system, Unix was a self-contained software system. This was one of the key reasons it emerged as an important teaching and learning tool and has had such a broad influence.

The inclusion of these components did not make the system large – the original V7 UNIX distribution, consisting of copies of all of the compiled binaries plus all of the source code and documentation occupied less than 10 MB and arrived on a single nine-track. The printed documentation, typeset from the online sources, was contained in two volumes. The names and filesystem locations of the Unix components have changed substantially across the history of the system. Nonetheless, the V7 implementation is considered by many to have the canonical early structure:. Kernel – source code in /usr/sys, composed of several sub-components:. conf – configuration and machine-dependent parts, including boot code.

dev – device drivers for control of hardware (and some pseudo-hardware). sys – operating system 'kernel', handling memory management, process scheduling, system calls, etc. Extends Unix design principles, and was developed as a successor to Unix The Unix system had significant impact on other operating systems. It achieved its reputation by its interactivity, by providing the software at a nominal fee for educational use, by running on inexpensive hardware, and by being easy to adapt and move to different machines.

Unix was originally written in (which had been thought necessary for system implementations on early computers), but was soon rewritten in, a. Although this followed the lead of and, it was Unix that popularized the idea. Unix had a drastically simplified file model compared to many contemporary operating systems: treating all kinds of files as simple byte arrays. The file system hierarchy contained machine services and devices (such as, or ), providing a uniform interface, but at the expense of occasionally requiring additional mechanisms such as and mode flags to access features of the hardware that did not fit the simple 'stream of bytes' model. The operating system pushed this model even further and eliminated the need for additional mechanisms. Unix also popularized the hierarchical file system with arbitrarily nested subdirectories, originally introduced by Multics. Other common operating systems of the era had ways to divide a storage device into multiple directories or sections, but they had a fixed number of levels, often only one level.

Several major proprietary operating systems eventually added recursive subdirectory capabilities also patterned after Multics. DEC's M's 'group, user' hierarchy evolved into directories, 's volumes evolved into 2.0+ subdirectories, and HP's group.account hierarchy and IBM's and library systems were folded into broader POSIX file systems.

Making the command interpreter an ordinary user-level program, with additional commands provided as separate programs, was another Multics innovation popularized by Unix. The used the same language for interactive commands as for scripting ( – there was no separate job control language like IBM's ). Since the shell and OS commands were 'just another program', the user could choose (or even write) their own shell. New commands could be added without changing the shell itself. Unix's innovative command-line syntax for creating modular chains of producer-consumer processes made a powerful programming paradigm widely available. Many later command-line interpreters have been inspired by the Unix shell.

A fundamental simplifying assumption of Unix was its focus on - text for nearly all file formats. There were no 'binary' editors in the original version of Unix – the entire system was configured using textual shell command scripts. The common denominator in the I/O system was the byte – unlike. The focus on text for representing nearly everything made Unix pipes especially useful, and encouraged the development of simple, general tools that could be easily combined to perform more complicated ad hoc tasks. The focus on text and bytes made the system far more scalable and portable than other systems. Over time, text-based applications have also proven popular in application areas, such as printing languages (, ), and at the application layer of the, e.g.,.

Unix popularized a syntax for that found widespread use. The Unix programming interface became the basis for a widely implemented operating system interface standard (POSIX, see above). The soon spread beyond Unix, and is now ubiquitous in systems and applications programming. Early Unix developers were important in bringing the concepts of and into practice, spawning a 'software tools' movement. Over time, the leading developers of Unix (and programs that ran on it) established a set of cultural norms for developing software, norms which became as important and influential as the technology of Unix itself; this has been termed the.

The were quickly implemented on the Unix versions widely used on relatively inexpensive computers, which contributed to the explosion of worldwide real-time connectivity, and which formed the basis for implementations on many other platforms. The Unix policy of extensive on-line documentation and (for many years) ready access to all system source code raised programmer expectations, and contributed to the 1983 launch of the. Free Unix and Unix-like variants. Console screenshots of (top, a popular ) and (bottom, a popular operating system) In 1983, announced the (short for 'GNU's Not Unix') project, an ambitious effort to create a system; 'free' in the sense that everyone who received a copy would be free to use, study, modify, and redistribute it. The GNU project's own kernel development project, had not yet produced a working kernel, but in 1991 released the as free software under the.

In addition to their use in the operating system, many GNU packages – such as the (and the rest of the ), the and the – have gone on to play central roles in other free Unix systems as well., consisting of the Linux kernel and large collections of compatible software have become popular both with individual users and in business. Popular distributions include,. A free derivative of Unix, was released in 1992 and led to the and projects. With the 1994 settlement of a lawsuit brought against the University of California and Berkeley Software Design Inc.

( ) by, it was clarified that Berkeley had the right to distribute BSD Unix for free, if it so desired. Since then, BSD Unix has been developed in several different product branches, including. Linux and BSD are increasingly filling the market needs traditionally served by proprietary Unix operating systems, as well as expanding into new markets such as the consumer desktop and mobile and embedded devices. Because of the modular design of the Unix model, sharing components is relatively common; consequently, most or all Unix and Unix-like systems include at least some BSD code, and some systems also include GNU utilities in their distributions.

In a 1999 interview, Dennis Ritchie voiced his opinion that Linux and BSD operating systems are a continuation of the basis of the Unix design, and are derivatives of Unix: 'I think the Linux phenomenon is quite delightful, because it draws so strongly on the basis that Unix provided. Linux seems to be the among the healthiest of the direct Unix derivatives, though there are also the various BSD systems as well as the more official offerings from the workstation and mainframe manufacturers.' In the same interview, he states that he views both Unix and Linux as 'the continuation of ideas that were started by Ken and me and many others, many years ago.' Was the open-source counterpart to developed by, which included a -licensed kernel and a primarily userland. However, discontinued the project upon their acquisition of Sun, which prompted a group of former Sun employees and members of the OpenSolaris community to fork OpenSolaris into the kernel. As of 2014, illumos remains the only active open-source System V derivative.

ARPANET In May 1975, described the development of Network Unix by the Center for Advanced Computation at the. The system was said to 'present several interesting capabilities as an mini-host'. At the time Unix required a license from that at $20,000(US) was very expensive for non- users, while an educational license cost just $150. It was noted that Bell was 'open to suggestions' for an ARPANET-wide license. Specific features found beneficial were the local processing facilities, a, efficient file system and access control, and unmountable volumes, unified treatment of peripherals as, integration of the (NCP) within the Unix file system, treatment of as special files that can be accessed through standard Unix, closing of all files on program exit, and the decision to be 'desirable to minimize the amount of code added to the basic Unix kernel'.

Branding. Running, a certified Unix operating system In October 1993, the company that owned the rights to the Unix System V source at the time, transferred the of Unix to the X/Open Company (now ), and in 1995 sold the related business operations to (SCO). Whether Novell also sold the to the actual software was the subject of a 2006 federal lawsuit, which Novell won. The case was appealed, but on August 30, 2011, the United States Court of Appeals for the Tenth Circuit affirmed the trial decisions, closing the case. Unix vendor accused Novell of. The present owner of the trademark UNIX is The Open Group, an industry standards consortium.

Only systems fully compliant with and certified to the qualify as 'UNIX' (others are called '). By decree of The Open Group, the term 'UNIX' refers more to a class of operating systems than to a specific implementation of an operating system; those operating systems which meet The Open Group's Single UNIX Specification should be able to bear the or trademarks today, after the operating system's vendor pays a substantial certification fee and annual trademark royalties to The Open Group. Systems licensed to use the UNIX trademark include, (formerly 'Digital UNIX', or ), and a part of. Notably, Inspur K-UX is a Linux distribution certified as UNIX 03 compliant. Sometimes a representation like Un.x,.NIX, or.N?X is used to indicate all operating systems similar to Unix. This comes from the use of the asterisk (.) and the question mark characters as wildcard indicators in many utilities. This notation is also used to describe other Unix-like systems that have not met the requirements for UNIX branding from the Open Group.

The Open Group requests that UNIX is always used as an adjective followed by a generic term such as system to help avoid the creation of a. Unix was the original formatting, but the usage of UNIX remains widespread because it was once typeset in ( Unix). According to, when presenting the original Unix paper to the third Operating Systems Symposium of the American (ACM), 'we had a new typesetter and had just been invented and we were intoxicated by being able to produce small caps.' Many of the operating system's predecessors and contemporaries used all-uppercase lettering, so many people wrote the name in upper case due to force of habit. It is not an acronym. Trademark names can be registered by different entities in different countries and trademark laws in some countries allow the same trademark name to be controlled by two different entities if each entity uses the trademark in easily distinguishable categories.

The result is that Unix has been used as a brand name for various products including book shelves, ink pens, bottled glue, diapers, hair driers and food containers. Several plural forms of Unix are used casually to refer to multiple brands of Unix and Unix-like systems. Most common is the conventional Unixes, but Unices, treating Unix as a noun of the, is also popular. The pseudo- plural form Unixen is not common, although occasionally seen., developer of the Solaris variant, has asserted that the term Unix is itself plural, referencing its many implementations. See also. and., and. References.

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External links The dictionary definition of at Wiktionary Media related to at Wikimedia Commons at Wikibooks., at. at the (archived April 8, 2015). at the (archived April 2, 2014). at. – a software perspective on the MC68000 CPU architecture and UNIX compatibility.