Unix (all-caps UNIX for the trademark) is a multitasking, multiuser computer operating system that exists in many variants. The original Unix was developed at AT&T's Bell Labs research center by Ken Thompson, Dennis Ritchie, and others.

Even Mac OSX is developed is a series of Unix-based graphical interface operating systems developed and marketed by Apple Inc.

Linux invented by Linus Torwalds , a finnish student as a project, which has grown to vast area of development where thousands of developers are been working upgrading the LINUX