What a Computer Does When You Turn it On

Have you ever wondered what happens when you press the power button on your computer?

Well, it’s pretty straight-forward, really. Your average PC or Mac is designed in such a way that the parts are interchangeable, so when it turns on, it has to check to see if any of its parts have been removed or replaced, or if new parts have been added. It does this by running a POST, a Power On Self Test.

It checks that all the necessary parts for operation are present, such as the CPU and the RAM memory, both of which are crucial to running the computer. It also needs the components for video, either on the main circuit board or a separate video card. If any of these items are missing or faulty, the computer halts its startup and there will be nothing displayed on the screen.

If they are present, it will continue to check and test everything, then, if everything is okay, pass control over to whatever operating system you have installed on your computer’s hard drive. This could be Windows or Linux, or if the computer is a Mac, it will be Mac OS.

The operating system (OS) is a program that acts as a middle-man between you and the computer, so that you can tell the computer what you want it to do. It talks to the computer’s hardware and other programs to make things happen.

If you want to know more about your computer and the basics of the operating system, check out the other tutorials on my site.

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