Unix 
A multiuser, multitasking operating system that is widely used in servers. Developed in 1969, Unix took off in the early 1970s as a general-purpose operating system. Since much of the Internet is hosted on Unix machines, the OS took on a new surge of popularity in the early 1990s. Unix was the first large-scale program to be written in the high-level programming language C. This means Unix can run on any computer that has a C compiler. This portability (and low cost) makes it widespread among universities. The Open Group holds the trademark on behalf of the industry and certifies software that confirms to the Unix standard. There are many versions of Unix, including IBM's OS/390, Hewlett-Packard's HP-UX, and Sun Solaris.