LINUX is modern , free operating system based on UNIX standards. It has been designed to run efficiently and reliably on common PC hardware, it run also on a variety of other platforms. It provides a programming interface and user interface compatible with standard UNIX systems.

A Complete Linux system includes many Components that were 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 a run time.

Linux is a multi-user system ,providing protection between processes and running multiple processes according to a time-sharing scheduler.

Inter-process communication is supported for message queues ,semaphores and shared memory and BSD’s socket interface.

Multiple networking protocols can be accessed simultaneously through the socket interface.

To the user, the file system appears as a hierarchical Directory tree that obeys UNIX semantics. Linux uses an abstraction layer to manage multiple different file system.

Device-oriented network and virtual file systems are supported. Device-oriented file-systems access disk storage through two caches.

The memory management system uses page sharing and copy-on-write to minimize the duplication of data shared by different processes. Pages are loaded on demand when they are first referenced, and are paged back out to backing store according to an LFU algorithm if physical memory needs to be reclaimed.