Operating Systems


In this section we will look at how operating systems work, the different types of operating systems and why an operating system is so important to your computer


An operating system is a piece of software which has several functions. Firstly the operating system acts as a platform for software to be installed on the computer. It allows the program access to the input and output devices on the computer which it needs to run and display. It also allocates system resources to programs so that they can run at the same time. For example, one program couldn’t have 100% of the resources or no other program would be able to run.


The operating system also allocates different resources to different users so that they can use the resources simultaneously in the case of a network operating system. Without an operating system it would be very difficult for the average user to use the computer. The operating system allows the user to control what the computer is dong, install programs, select files and documents and organise the things that are installed. For example, in Windows, the start-menu is a key part of the operating system’s design and without it users would not have such easy control of the system.


Ocassionally a piece of hardware or software will need the attention of the CPU without the user's control. To do this, the CPU could check every so often whether each device needs attention. This is called 'polling'. However, polling is like picking up the phone every minute to see if anyone has called you. An easier way is by using 'interrupts'.



1) Define two different types of operating system

2) Explain the difference between hardware and software interrupts