LINUX/UNIX has three most important parts. They are Kernel, Shell and File System


Figure: Layers of Linux


  • Kernel is the heart of the operating system.
  • It is the low level core of the System that is the interface between applications and H/W.
  • Functions
  • Manage Memory, I/O devices, allocates the time between user and process,inter process communication, sets process priority


The shell is a program that sits on the as an interface between users and kernel It is a command interpreter and also has programming capability of its own.

  • Shell Types
  • Bourne Shell (sh) (First shell by Stephen Bourne)
  • C Shell(sh)
  • Korn Shell (ksh)
  • Bourne Again Shell(bash)

File System

  • Linux treats everything as a file including hardware devices. Arranged as a directory hierarchy.
  • The top level directory is known as ―root (/).