AT&T

AT&T (American Telephone and Telegraph) is one of the largest telecommunications providers in the United States. It is also noted for being the birthplace of the Unix operating system, and the C and programming languages.. 2002-06-21.
==History==
AT&T was incorporated in 1885, but traces its lineage to and his invention of the telephone in 1876. As parent company of the former , AT&T's primary mission was to provide telephone service to virtually everyone in the United States. In its first 50 years, AT&T established subsidiaries and allied companies in more than a dozen other countries. It sold these interests in 1925 and focused on achieving its mission in the United States. It did, however, continue to provide international long distance service.
The Bell System was dissolved at the end of 1983 with AT&T's divestiture of the Bell telephone companies. AT&T split into three parts in 1996, one of which is , the former systems and equipment portion of AT&T (including ).
==Wireless services==
AT&T's 2G and 3G services were based on GSM and its derivative UMTS, respectively.AT&T GSM Network Technology (PDF), AT&T. 2008-05-20. was the iPhone's first exclusive carrier until February 10, 2011, when rival carrier Verizon released a CDMA-capable iPhone 4, ending Apple's exclusivity agreement with AT&T.Verizon Wireless Finally Gets Apple's iPhone by Sam Gustin, Wired. 2011-01-11.
===Apple devices exclusively carried by AT&T===
*iPhone
*iPhone 3G
*iPhone 3GS
*iPhone 4 (GSM version)
*iPad
*iPad 2 (GSM version)
===Retirement of 3G service===
AT&T shut down its GSM-based 3G network on February 22, 2022 to make room for faster 4G and 5G services.Act now - 3G is going away in 2022, AT&T. 2021-09-09.Plan Ahead for Phase Out of 3G Cellular Networks and Service, Federal Communications Commission. 2021-08-23. This affected all older iPhone models that do not support (iPhone 5C, 5S and earlier). This also affected the 3G-enabled original iPad and iPad 2.Devices Working on AT&T Network (PDF), AT&T. 2021-09-03.
==References==
==External links==
*AT&T official website
*AT&T Services apps at the Apple App Store
* at Wikipedia
Category:Companies
Category:Networks
Category:1885 establishments