What is an operating system?

Hi Betty,

In school I am taking a class call the Fundamentals of Operating Systems.

If I understand it right an operating system is like Windows Vista. And the operating system is the brain of the computer because it makes everything work together. Example: mouse, keyboard, monitor, and printer. It controls what is put into the computer and what comes out. Like when you strick a key on the keyboard it is the input and then when you see the typing on the screen this is the output.

Does this make any sense to you Betty? Am I understanding what an operating system is and what it does?

I am also taking a Unix class.
– Mary


You are correct – Windows Vista is an operating system.  So is Windows XP, Windows 2000, Windows 98, MAC OSx, MAC OSx v10, Fedora (linux), HPUX (Unix), AIX (Unix) and numerous others.  All of the last six that I mentioned are Unix-based.

You are also correct in saying that the keyboard is an input device and the screen is an output device; in fact – these are the default input / output devices.

However, you are not correct in referring to the operating system as the ‘brain’ of the computer.  It is not.

Let me explain:

Examples of input devices:
Keyboard (the default)

Examples of output devices:
Screen (this is the default)

Computers transmit data in binary.  Binary has just two characters; 1 or 0.  Think of it as a light switch.  On or Off.

Now, if you could look at a motherboard (the main circuit board) of the computer – you would see that it looks like a roadmap.  And its function is much the same.  Except that it has ‘gates’ that allow the data to pass through or divert in another direction.  If the data being sent to it is “ON”, it opens the gate.  If it is “OFF”, it closes the gate – and the data takes a different path.

All of the data put INTO the computer is handed from the input device to a driver or controller – who then ‘drives’ it down the road to the central processing unit (CPU).  The CPU looks at it and says “What do you want me to do with this?”, makes a decision, and then sends it on down the road – to the appropriate output device.  Sometimes it has to pass through several gates to get to its destination.

So .. the CPU is the brain.  It reads the input and decides what the output should be.  It makes that decision.

Now, to get back to your original question – what is the operating system?  What purpose does it serve?

The Operating system is the interface between YOU and the computer.  You push the button, you move the mouse, you speak into the microphone .. .YOU tell the computer what you want it to do.  The operating system is a software program that takes your input and translates it into something the computer will understand.  It makes it easy for you to use the computer.

Hope this helps!