AT&T

American Telephone and Telegraph Company

History
In 1991 AT&T bought National Cash Register (NCR).

Operating Systems

 * Bell Laboratories: UNIX
 * Plan 9

Programming Languages

 * C
 * C++

Open Source

 * AT&T Software Technology (AST) toolkit
 * UWIN - UNIX application build environement for Microsoft Windows

Links

 * https://github.com/att