• Miss S

Oodles of Operating Sytems [GCSE]


Multitasking operating systems run on standalone computers, and are the operating systems we use on a day to day basis. Using windows as an example, when we are using the computer, we can have multiple applications open at once. This could be in any combination such as:

  • Having a VOIP software, video game and web browser running at the same time

  • Having a word processor, web browser, and e-book reader open at the same time

  • Using a calculator, spreadsheet software and conferencing software at the same time

Or any other combination!

Even though these might appear to be running at the same time, the CPU switches its attention between each process fast enough so the user doesn’t notice that actually only one program is running at a time. We can open the task manager to see all of the programs running, but only one will currently be active in the CPU. It is the operating system’s job to ensure that the CPU is as busy as possible, hence the impression that multiple programs are running at once - the CPU will never stand idle waiting for a task to complete.

Real-time Operating Systems

Real-time operating systems are those that require fixed time, reliable processing of information. These systems are often used in safety critical systems such as aeroplanes, hospitals, chemical plants or manufacturing facilities. Real-time operating systems are often embedded systems, but with the following benefits

  • They must have a strategy for redundancy. If one piece of hardware fails, the operating system has to facilitate an automatic shift to backup hardware. Imagine if you were on an aeroplane, if the navigation processor stopped working, I’m sure you would want it to switch to a backup rather than your plane getting lost. This is an essential component of real-time operating systems.

  • Real-time operating systems must take in the input from multiple sources at the same time. Going with the aeroplane example once more, they must take the input of sensors, pilot controls, customer requests, air traffic commands all at the same time. If the operating system couldn’t process these at the same time, the entire operation would fail.

  • Alongside the incorporation of redundancy, they must have a fail safe mechanism. This will allow the system to detect if a piece of hardware fails. If it does, appropriate action will need to be taken.

  • Any processing in real-time operating systems must be performed in a fraction of a second. This has to be a guaranteed time frame, as these systems literally have a significant impact on people’s lives.

Multi-user Operating Systems

Multi-user operating systems allow many users to log in and use the same system at the same time. This operating system isn’t just responsible for scheduling one person’s programs, memory and files, but is responsible for doing this for potentially hundreds users at the same time. Most multi-user systems are also multitasking systems.

Food for thought: What sort of computers do you think your computers at school use?

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