UNIX

A powerful multi-tasking, multi-user computer operating system (OS). UNIX was developed at

AT&T Bell Telephone Laboratories during the years 1969 to 1973 by Ken Thompson and Dennis Ritchie for minicomputer application. As UNIX is written in the highly portable C programming language, it is used on a wide variety of computers, from mainframes to PDAs. A number of UNIX variations have been developed, some of which are available as freeware, and are known as Linux. See also Bell Labs, freeware, Linux, mainframe computer, minicomputer, OS, PDA, and portability.

• pseudoquaternary coding
• pseudorandom noise (PN)
• pseudowire
• pseudowire emulation edge to edge (PWE3)
• pseudowire emulation (PWE)
• PSK (Phase-Shift Keying)
• PSP (Payphone Service Provider)
• PSQM (Perceptual Speech Quality Measurement)
• PSQM+ (Perceptual Speech Quality Measurement plus)
• PSS1 (Private Signaling System No. 1)
• PSTN (Public Switched Telephone Network)
• PSTS (Public Switched Telephone System)
• PTE (Path Terminating Equipment)
• PTI (Payload Type Indicator)
• PTT
• PTT
• public data network (PDN)
• public domain
• public IP address
• public key encryption
• public key infrastructure (PKI)
• Public Safety Access Point (PSAP)
• Public Service Commission (PSC)
• public switched telephone network (PSTN)
• public switched telephone system (PSTS)