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Operating systems

An operating system (OS) is the most important piece of software on your computer. It is the program that runs and manages your computer. This involves quite a few different jobs.

It makes sure all of the hardware and peripherals are working together without a problem.
It organises the software and files on your computer.
It manages you RAM so that programs are run successfully.
It is responsible for keeping your computer secure.
It provides you with a user interface, so you can actually use the computer.

os logosYou probably know the names of some operating systems. These include Windows (Windows XP, Windows Vista, Windows 7, Windows 8), Linux, Ubuntu, iOS, Android, Chrome OS, Chromium OS and so on. If you do a search online, you can find out about lots of them and the strengths and weaknesses of each type of operating system compared to other the types. 

Booting up your computer and your user interface
When you boot-up your computer, the program in ROM carries out the Power On Self Test (POST) to check your computer is working correctly. Then it finds the operating system on the hard drive, copies it into RAM and hands over control to the operating system. The operating system then takes over. Some programs e.g. your virus checker, you have probably set to start automatically, so the operating system will start that program running. It will then display a 'user interface' on your monitor. It will display buttons and icons and words that you can click on, double-click, right-click and so on. You can now access the computer. We don't know how any of those complicated bits of hardware work, but we do know how to use a keyboard and mouse and click on things - that's what the user interface lets you do. It's the mouse, the keyboard, the touchscreen and what you see on your screen, all working together.

Making the hardware work togetheruser interface
The operating system makes all of the hardware work together. If there is a problem, it will try to fix it or give you an error message to help you fix it. If you decide to plug a new piece of equipment into your computer e.g. a printer or a pen drive, the operating system will detect that you have done this, check it can work with it, load up any additional software it needs and then tell you that you can use it.

Organising applications and files
When you load up software, the operating system organises where they will be stored on the hard disk. You might tell the computer what folder to put some software in, but ultimately, in the background, the operating system is organising it all. It's the same with your files. When you save a file, you might put it in a folder. That's you using the user interface but in the background, the operating system is actually deciding where and how to organise your work. You see your 'human' view of organised folders and files but the operating system works in the background to save things as it needs to.

Running programs
You might have lots of different programs running at once. These might include a virus checker, a music program, a chatroom, a web browser and so on. As you know, programs must be in RAM for the CPU to be able to run them. They must be organised in RAM in such a way so that they don't interfere with each other and make a program or the computer crash. Guess what? It's the operating system's job to manage the memory so that programs and files are nicely organised when they are copied into RAM.

login2Security
The operating system will try to keep the computer safe and keep everyone's files safe. It might do this with some extra 'helping' software like a virus checker but ultimately, it's responsible for security. One job it does, for example, is to allow you to set up different accounts on the same computer, each with their own login and password. When someone logs in, they will only be able to see their own files and software and any that are public. They won't be able to see anyone else's files. The computer will also be set up with the settings for that user, so that it looks the way they want it. For example, it will have their own personal wallpaper as the background on the monitor.

Q1. What is meant by a 'peripheral'? Give 5 examples of peripherals.
Q2. Describe what the operating system does when you plug in a peripheral.
Q3. Where is the operating system when the power is switched off a computer?
Q4. What is meant by a 'user interface'?
Q5. Name five different operating systems, apart from any Windows operating systems.
Q6. How does an operating system control access to a computer for different users?
Q7. Operating systems are responsible for 'memory management'. What is meant by this?
Q8. What operating system does your phone use? What about your computer at home? If you have a tablet computer, what OS does that use?
Q9. Some operating systems are free and some have to be paid for. When you buy a computer, if it comes with certain operating systems, they will have been included in the whole price. Give an example of an operating system that you would have to buy and one that is free to download and use by anyone.
Q10. Some software, including some operating systems, can be described as 'open source'. What does this mean?

Extension work
a) When reading about operating systems, you might see the word 'kernel' mentioned. What does this refer to?
b) Windows has millions of fans but Linux users think that the Linux OS is better. Do some research. Find out the key pros and cons in the Windows V Linux debate.

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