UNIX is a computer operating system – the base software that controls a computer system and its peripherals. In this sense, UNIX behaves in the same way that the perhaps more familiar PC operating systems Windows or MacOS behave. It provides the base mechanisms for booting a computer, logging in, running applications, storing and retrieving files, etc.
More specifically, the word “UNIX” refers to a family of operating systems that are related to one or both of the original UNIX operating systems – BSD and SystemV. Examples of modern UNIX operating systems include IRIX (from SGI), Solaris (from Sun), Tru64 (from Compaq) and Linux (from the Free Software community). Even though these different “flavors” of UNIX have unique characteristics and come from different sources, they all work alike in a number of fundamental ways.
It was designed from the ground up to be a multi-user, shared, networked operating environment. UNIX has concepts such as Users, Groups, Permissions and Network-Shared Resources (such as files, printers, other computer systems, etc.) built-in to the core of its design. This makes UNIX a uniquely powerful and flexible operating system.
LINUX is a modern, free operating system based on UNIX standards.It has been designed to run efficiently and reliably on common PC hardware;it also runs on a variety of other platforms.It provides a programming interface compatible with standard UNIX systems and can run a large number of UNIX applications,including an increasing number of commercially supported applications.
Linux has not evolved in a vacuum.A complete Linux system includes many components that were developed independently of Linux.The core Linux operating system kernel is entirely original,but,it allows much existing free UNIX software to run,resulting in an entire UNIX-compatible operating system free from proprietary code.
The Linux kernel is implemented as a traditional monolithic kernel for performance reasons,but,it is modular enough in design to allow most drivers to be dynamically loaded and unloaded at run time.
Linux is a multiuser system,providing protection between processes and running multiple processes according to time-sharing scheduler.Newly created processes can share selective parts of their execution environment with their parent processes,allowing multithreaded programming.Internally,Linux uses an abstraction layer to manage multiple different file system.