is the best-known and most-used open source
operating system. As an operating system, Linux is software that sits underneath all of the other software on a computer, receiving requests from those programs and relaying these requests to the computer’s hardware.Unix
is a portable, multitasking, multiuser, time-sharing operating system (OS) originally developed in 1969 by a group of employees at AT&T. Unix was first programmed in assembly language but was reprogrammed in C in 1973.
Unix has been ported to more machine families than any other operating system. As a result, it has come to be identified with the concept of open systems. Unix operating systems are widely used in PCs, servers and mobile devices. The Unix environment was also an essential element in the development of the Internet and networking.