AT&T Inc. is an American multinational conglomerate holding company headquartered at Whitacre Tower in Downtown Dallas, Texas. It is the world's largest telecommunications company, the second largest provider of mobile telephone services, the largest provider of fixed telephone services in the United States through AT&T Communications. Since June 14, 2018, it is the parent company of mass media conglomerate WarnerMedia, making it the world's largest media and entertainment company in terms of revenue; as of 2018, AT&T is ranked #9 on the Fortune 500 rankings of the largest United States corporations by total revenue. AT&T began its history as Southwestern Bell Telephone Company, a subsidiary of the Bell Telephone Company, founded by Alexander Graham Bell in 1880; the Bell Telephone Company evolved into American Telephone and Telegraph Company in 1885, which rebranded as AT&T Corporation. The 1982 United States v. AT&T antitrust lawsuit resulted in the divestiture of AT&T Corporation's subsidiaries or Regional Bell Operating Companies, resulting in several independent companies including Southwestern Bell Corporation.
In 2005, SBC purchased its former parent AT&T Corporation and took on its branding, with the merged entity naming itself AT&T Inc. and using its iconic logo and stock-trading symbol. In 2006, AT&T Inc. acquired BellSouth, the last independent Baby Bell company, making their joint venture Cingular Wireless wholly owned and rebranding it as AT&T Mobility. The current AT&T reconstitutes much of the former Bell System, includes ten of the original 22 Bell Operating Companies along with the original long distance division. AT&T can trace its origin back to the original Bell Telephone Company founded by Alexander Graham Bell after his patenting of the telephone. One of that company's subsidiaries was American Telephone and Telegraph Company, established in 1885, which acquired the Bell Company on December 31, 1899, for legal reasons, leaving AT&T as the main company. AT&T established a network of subsidiaries in the United States and Canada that held a government-authorized phone service monopoly, formalized with the Kingsbury Commitment, throughout most of the twentieth century.
This monopoly was known as the Bell System, during this period, AT&T was known by the nickname Ma Bell. For periods of time, the former AT&T was the world's largest phone company. In 1982, U. S. regulators broke up the AT&T monopoly, requiring AT&T to divest its regional subsidiaries and turning them each into individual companies. These new companies were known as Regional Bell Operating Companies, or more informally, Baby Bells. AT&T continued to operate long distance services, but as a result of this breakup, faced competition from new competitors such as MCI and Sprint. Southwestern Bell was one of the companies created by the breakup of AT&T Corp; the architect of divestiture for Southwestern Bell was Robert G. Pope; the company soon started a series of acquisitions. This includes the 1987 acquisition of Metromedia mobile business and the acquisition of several cable companies in the early 1990s. In the half of the 1990s, the company acquired several other telecommunications companies, including some Baby Bells, while selling its cable business.
During this time, the company changed its name to SBC Communications. By 1998, the company was in the top 15 of the Fortune 500, by 1999 the company was part of the Dow Jones Industrial Average. In 2005, SBC purchased AT&T for $16 billion. After this purchase, SBC adopted the better-known AT&T name and brand, with the original AT&T Corp. still existing as the long-distance landline subsidiary of the merged company. The current AT&T claims the original AT&T Corp.'s history as its own, though its corporate structure only dates from 1983. It retains SBC's pre-2005 stock price history, all regulatory filings prior to 2005 are for Southwestern Bell/SBC, not AT&T Corp. In September 2013, AT&T Inc. announced it would expand into Latin America through a collaboration with América Móvil. In December 2013, AT&T announced plans to sell its Connecticut wireline operations to Stamford-based Frontier Communications. AT&T purchased the Mexican carrier Iusacell in late 2014, two months purchased the Mexican wireless business of NII Holdings, merging the two companies to create AT&T Mexico.
In July 2015, AT&T purchased DirecTV for $48.5 billion, or $67.1 billion including assumed debt, subject to certain conditions. AT&T subsequently announced plans to converge its existing U-verse home internet and IPTV brands with DirecTV, to create AT&T Entertainment. In an effort to increase its media holdings, on October 22, 2016, AT&T announced a deal to buy Time Warner for $108.7 billion. AT&T owns a 2% stake in Canadian-domiciled entertainment company Lionsgate. On July 13, 2017, it was reported that AT&T would introduce a cloud-based DVR streaming service as part of its effort to create a unified platform across DirecTV and its DirecTV Now streaming service, with U-verse to be added soon. In October 2018, it was announced that the service Is set to launch in 2019On September 12, 2017, it was reported that AT&T planned to launch a new cable TV-like service for delivery over-the-top over its own or a competitor's broadband network sometime next year. On November 20, 2017, Assistant Attorney General Makan Delrahim filed a lawsuit for the United States Department of Justice Antitrust Division to block the merger with Time Warner, saying it "will harm competition, result in higher bills for consumers and less innovation."
In order for AT&T to acquire Time Warner, the Department of Justice stated that the company must
Berkeley Software Distribution
The Berkeley Software Distribution was an operating system based on Research Unix and distributed by the Computer Systems Research Group at the University of California, Berkeley. Today, "BSD" refers to its descendants, such as FreeBSD, OpenBSD, NetBSD, or DragonFly BSD. BSD was called Berkeley Unix because it was based on the source code of the original Unix developed at Bell Labs. In the 1980s, BSD was adopted by workstation vendors in the form of proprietary Unix variants such as DEC Ultrix and Sun Microsystems SunOS due to its permissive licensing and familiarity to many technology company founders and engineers. Although these proprietary BSD derivatives were superseded in the 1990s by UNIX SVR4 and OSF/1 releases provided the basis for several open-source operating systems including FreeBSD, OpenBSD, NetBSD, DragonFly BSD, TrueOS. These, in turn, have been used by proprietary operating systems, including Apple's macOS and iOS, which derived from them, Microsoft Windows, which used a part of its TCP/IP code.
The earliest distributions of Unix from Bell Labs in the 1970s included the source code to the operating system, allowing researchers at universities to modify and extend Unix. The operating system arrived at Berkeley in 1974, at the request of computer science professor Bob Fabry, on the program committee for the Symposium on Operating Systems Principles where Unix was first presented. A PDP-11/45 was bought to run the system, but for budgetary reasons, this machine was shared with the mathematics and statistics groups at Berkeley, who used RSTS, so that Unix only ran on the machine eight hours per day. A larger PDP-11/70 was installed at Berkeley the following year, using money from the Ingres database project. In 1975, Ken Thompson came to Berkeley as a visiting professor, he started working on a Pascal implementation for the system. Graduate students Chuck Haley and Bill Joy improved Thompson's Pascal and implemented an improved text editor, ex. Other universities became interested in the software at Berkeley, so in 1977 Joy started compiling the first Berkeley Software Distribution, released on March 9, 1978.
1BSD was an add-on to Version 6 Unix rather than a complete operating system in its own right. Some thirty copies were sent out; the second Berkeley Software Distribution, released in May 1979, included updated versions of the 1BSD software as well as two new programs by Joy that persist on Unix systems to this day: the vi text editor and the C shell. Some 75 copies of 2BSD were sent out by Bill Joy. A VAX computer was installed at Berkeley in 1978, but the port of Unix to the VAX architecture, UNIX/32V, did not take advantage of the VAX's virtual memory capabilities; the kernel of 32V was rewritten by Berkeley students to include a virtual memory implementation, a complete operating system including the new kernel, ports of the 2BSD utilities to the VAX, the utilities from 32V was released as 3BSD at the end of 1979. 3BSD was alternatively called Virtual VAX/UNIX or VMUNIX, BSD kernel images were called /vmunix until 4.4BSD. After 4.3BSD was released in June 1986, it was determined that BSD would move away from the aging VAX platform.
The Power 6/32 platform developed by Computer Consoles Inc. seemed promising at the time, but was abandoned by its developers shortly thereafter. Nonetheless, the 4.3BSD-Tahoe port proved valuable, as it led to a separation of machine-dependent and machine-independent code in BSD which would improve the system's future portability. In addition to portability, the CSRG worked on an implementation of the OSI network protocol stack, improvements to the kernel virtual memory system and new TCP/IP algorithms to accommodate the growth of the Internet; until all versions of BSD used proprietary AT&T Unix code, were therefore subject to an AT&T software license. Source code licenses had become expensive and several outside parties had expressed interest in a separate release of the networking code, developed outside AT&T and would not be subject to the licensing requirement; this led to Networking Release 1, made available to non-licensees of AT&T code and was redistributable under the terms of the BSD license.
It was released in June 1989. After Net/1, BSD developer Keith Bostic proposed that more non-AT&T sections of the BSD system be released under the same license as Net/1. To this end, he started a project to reimplement most of the standard Unix utilities without using the AT&T code. Within eighteen months, all of the AT&T utilities had been replaced, it was determined that only a few AT&T files remained in the kernel; these files were removed, the result was the June 1991 release of Networking Release 2, a nearly complete operating system, distributable. Net/2 was the basis for two separate ports of BSD to the Intel 80386 architecture: the free 386BSD by William Jolitz and the proprietary BSD/386 by Berkeley Software Design. 386BSD itself was short-lived, but became the initial code base of the NetBSD and FreeBSD projects that were started shortly thereafter. BSDi soon found itself in legal trouble with AT&T's Unix System Laboratories subsidiary the owners of the System V copyright and the Unix trademark.
The USL v. BSDi lawsuit was filed in 1992 and led to an injunction on the distribution of Net/2 until the validity of USL's copyright claims on the source could be determined; the lawsuit slowed development of the free-
UNIX System V
UNIX System V is one of the first commercial versions of the Unix operating system. It was developed by AT&T and first released in 1983. Four major versions of System V were released, numbered 1, 2, 3, 4. System V Release 4, or 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; as of 2012, the Unix market is divided between five System V variants: IBM's AIX, Hewlett-Packard's HP-UX, Oracle's Solaris, Xinuos's UnixWare and illumos distributions being the open-source OpenSolaris continuation. System V was the successor to 1982's UNIX System III. While AT&T sold their own hardware that ran System V, most customers instead ran a version from a reseller, based on AT&T's reference implementation. A standards document called the System V Interface Definition outlined the default features and behavior of implementations.
During its formative years, AT&T went through several phases of System V software groups, beginning with the Unix Support Group, followed by Unix System Development Laboratory, followed by AT&T Information Systems, Unix System Laboratories. In the 1980s and early-1990s, System V was considered one of the two major versions of UNIX, the other being the Berkeley Software Distribution. BSD was commonly called "BSD Unix" or "Berkeley Unix". Eric S. Raymond summarizes the longstanding relationship and rivalry between System V and BSD during the early period: In fact, for years after divestiture the Unix community was preoccupied with the first phase of the Unix wars – an internal dispute, the rivalry between System V Unix and BSD Unix; the dispute had several levels, some technical and some cultural. The divide was between longhairs and shorthairs. While HP, IBM and others chose System V as the basis for their Unix offerings, other vendors such as Sun Microsystems and DEC extended BSD. Throughout its development, System V was infused with features from BSD, while BSD variants such as DEC's Ultrix received System V features.
AT&T and Sun Microsystems worked together to merge System V with BSD-based SunOS to produce Solaris, one of the primary System V descendants still in use today. Since the early 1990s, due to standardization efforts such as POSIX and the commercial success of Linux, the division between System V and BSD has become less important. System V, known inside Bell Labs as Unix 5.0, succeeded AT&T's previous commercial Unix called System III in January, 1983. There was never an external release of Unix 4.0, which would have been System IV. This first release of System V was developed by AT&T's UNIX Support Group and based on the Bell Labs internal USG UNIX 5.0. System V included features such as the vi editor and curses from 4.1 BSD, developed at the University of California, Berkeley. It added support for inter-process communication using messages and shared memory, developed earlier for the Bell-internal CB UNIX. SVR1 ran on DEC VAX minicomputers. AT&T's UNIX Support Group transformed into the UNIX System Development Laboratory, which released System V Release 2 in 1984.
SVR2 added shell functions and the SVID. SVR2.4 added demand paging, copy-on-write, shared memory, record and file locking. The concept of the "porting base" was formalized, the DEC VAX-11/780 was chosen for this release; the "porting base" is the so-called original version of a release, from which all porting efforts for other machines emanate. Educational source licenses for SVR2 were offered by AT&T for US$800 for the first CPU, $400 for each additional CPU. A commercial source license was offered for $43,000, with three months of support, a $16,000 price per additional CPU. Apple Computer's A/UX operating system was based on this release. SCO XENIX used SVR2 as its basis; the first release of HP-UX was an SVR2 derivative. Maurice J. Bach's book, The Design of the UNIX Operating System, is the definitive description of the SVR2 kernel. AT&T's UNIX System Development Laboratory was succeeded by AT&T Information Systems, which distributed UNIX System V, Release 3, in 1987. SVR3 included STREAMS, the Remote File System, the File System Switch virtual file system mechanism, a restricted form of shared libraries, the Transport Layer Interface network API.
The final version was Release 3.2 in 1988, which added binary compatibility to Xenix on Intel platforms. User interface improvements included the "layers" windowing system for the DMD 5620 graphics terminal, the SVR3.2 curses libraries that offered eight or more color pairs and other at this time important features. The AT&T 3B2 became the official "porting base." SCO UNIX was based upon SVR3.2. Among the more obscure distributions of SVR3.2 for the 386 were ESIX 3.2 by Everex and "System V, Release 3.2" sold by Intel themselves. IBM's AIX operating system is an SVR3 derivative. System V Release 4.0 was announced on October 18, 1988 and was incorporated into a variety of commercial Unix products from early 1989 onwards. A joint project of AT&T Unix System Laboratories and Sun Microsystems, it combined technology from: SVR3 4.3BSD Xenix SunOSNew features