Architecture of Unix

After a brief introduction about the features of Unix, its time that we know the basic functioning of the Unix operating system. Have you ever thought how does your computer turns OFF when you press the 'Shutdown' button in your computer. If you know, its good, but anyways let me explain it.  When you press or click on the SHUTDOWN button of your computer, the program written for that shutdown interacts with the hardware of the computer and that generates a series of electrical signals that turn off your computer.
Similarly the architecture of Unix is somewhat like. There are prewritten routines for each command and the Unix Operating system interacts with the hardware through a complex mechanism.
Take a careful look at the figure below.

Architecture Of Unix

In the above figure, you see USER at the top most , then APPLICATION below that, then SHELL, KERNEL, and finally HARDWARE. We take a look at each of these terms now.


USER :  The end user is you, that is the person who is going to use the Unix machine


APPLICATION :  The prewritten commands and routines in Unix are the applications. It may be possible that you install your own softwares in your Unix/Linux system and then they will become part of the applications. These applications are computer programs that help you do a job, say for example a ping-pong flash game is an application that helps you play ping pong game in your computer. Similarly the flash is also an application program.

SHELL :  A shell is the most critical part of the Unix operating system. It is a sort of interpreter between you and the Unix system. it helps you do waht you want, and if it cannot interpret what you want to do it will throw you a 'SYNTAX ERROR' message !  Its main function is to interpret the command given by the user, communicate the same to the system and give you the output. It is a program written and stored in the Unix file system.

KERNEL :  The kernel is the heart of Unix which has got most of the responsibilities of managing and utilising the hardware resources available to Unix Operating System, like memory management, CPU scheduling, disk management , power management etc. The 'Shell' talks to the Hardware through the 'Kernel', and so the Unix functions.

HARDWARE :  Finally this is the visual things that you see in front of you , the CPU, the keyboard, monitor etc.