Things you may want to know but you don’t have to know

Stories of Two Companies AT&T Digital Equipment Corporation

AT&T Alexander Graham Bell Invented the telephone system. Founded the American Telephone and Telegraph Company (AT&T) in 1885.

AT&T AT&T became the world’s largest telephone company. It employed one million people and its revenue was $3 billion annually. In 1984, US government divided AT&T into 8 companies including original AT&T. AT&T – long distance services 7 Baby Bells – local services

7 Baby Bells Bell Atlantic NYNEX Southwestern Bell Ameritech BellSouth Pacific Telesis US West

7 Baby Bells Bell Atlantic => Verizon NYNEX Southwestern Bell => SBC Ameritech BellSouth Pacific Telesis US West

7 Baby Bells Bell Atlantic => Verizon NYNEX Southwestern Bell => SBC => AT&T Ameritech BellSouth Pacific Telesis US West => Qwest => CenturyLink

Digital Equipment Corporation (DEC) Leading Computer Vendor from 1950s to 1990s. PDP-11, VAX-11 minicomputers, etc.

DEC was acquired by Compaq in 1998. Compaq was merged with HP.

Why do we talk about these companies? The UNIX operating system was developed by Ken Thompson and Dennis Ritchie in Bell Labs research center. It was implemented on DEC PDP-7. The code was written in Assembly language and C.

What is an Operating System? I/O system Instr. Set Proc. Compiler Operating System Application Digital Design Circuit Design Firmware Datapath & Control Layout

What is an Operating System? It controls all the computer’s resources (processor(s), memory, input, output, etc.) It provides the base upon which application programs can be written. Without an OS, a computer cannot perform nothing. Unix, Linux, Windows, MacOS, iOS, Android, …

2017 Top Programming Languages – IEEE Spectrum

Terms bit, byte, word KB, MB, GB, TB, PB, EB, ZB, YB… https://en.wikipedia.org/wiki/File_size sec, ms, us, ns, ps