Answer:
see below
Explanation:
Process management - If you have some cpu, gpu, ram, and storage you technically do have a computer but what is going to run and coordinate all the individual tasks you throw at it, that is the operating system's job. I personally like the analogy that the computers physical parts are players on a baseball field, and the operating system are all the coaches and team coordinators. process management is responsible for memory management, disk management and networking.
Security - For a computer to have the ability to be secure it needs to have some sort of management, in comes the analogy of the coaches, that means the operating system is also necessary for device security. That means stopping hackers from accessing your computer remotely, malicious links, and buggy code from corrupting the system just as a few examples. For security to work the computer also has to keep drivers up to date, to prevent malfunctions with external devices or to make them work at all. You know when your printer isn't working with your computer, that is most likely a driver error, and that means the computer isn't being able to properly communicate with the printer and send it commands which is exactly what drivers do.
Graphical User interface - also know as "GUI" this make it so that the computer has tangible clickable items, if operating system's did not have integrated user interfaces we would all have to use command lines which are more complicated for daily use.
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Those are all the major functions of an Operating System or "OS" I tried not to be too complicated but trying to explain in an easy way is not easy especially when we are talking about the "OS,'' which is basically 50% of a computer.
