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Operating Systems

Operating Systems. Mr David Royall. An operating system is a software program that controls and organises the general operation of the computer. A computer cannot work without an operating system. In ALL computers, the next few slides explain the operating system will have to do.

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Operating Systems

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  1. Operating Systems Mr David Royall

  2. An operating system is a software program that controls and organises the general operation of the computer. A computer cannot work without an operating system. • In ALL computers, the next few slides explain the operating system will have to do Operating system functions

  3. control the backing store and peripherals such as disk drives and printers • control the loading and running of programs • organise the use of memory between programs Functions (1)

  4. organise processing time between programs and users • organise priorities between programs and users • maintain security and access rights of users • deal with errors and user instructions Functions (2)

  5. deal with the transfer of programs in and out of memory • allow the user to save files to a backing store • control the transfer of datato peripherals such as printers • provide the interfacebetween user and computer - for example, Windows XP, Windows Vista and OSX. • issue simple error messages Functions on a PC

  6. In a larger computer such as a main framethe operating system works on the same principles. Main frame is A powerful multi-user computer capable of supporting many hundreds or thousands of users simultaneously Functions on a Large Computer

  7. Computers can operate in many different ways requiring different and complex operating systems. The Operating Systems are: • Real time processing • Multi-Programming • Multi-Tasking • Multi-Access or Multi-User • Batch Processing Modes of operation

  8. When the computer has to react within a guaranteed time to an input, a real time operating system is used. • Example (1), the engine management system within a car uses a real time operating system in order to react to all the things going on within the engine. • A real time operating system does not necessarily have to be fast. It simply has to be quick enough to respond to inputs in a predictable way. • Embedded computers often contain an RTOS as many are used to control something. • Computers operating in real time are often dedicated to the control of systems such as industrial processes, planes and space flights. • Example (2) of real time processing is computer games. When an action is selected in a game, the data is fed back to the computer and the systems updated. Real time processing

  9. Multi-programming is a method of operating such that several programs appear to be running at once. • The jobs are usually given priorities. • The operating systemswitches jobs in and out of processor time according to priority. • Example: while one job is being allocated printer time, another will be being processed in memory. • The processoris so fast that it seems that many jobs are being processed at the same time. Multi-programming

  10. This isn't just about running more than one application at the same time. Multi-tasking allows multiple tasks to run concurrently, taking turns using the resources of the computer. • This can mean running a couple of applications, sending a document to the printer and downloading a web page. • However, operating systems are not truly multi-tasking - in order to do this, you would need parallel processors, which are now appearing on personal computers. Multi-tasking

  11. A multi-access (or multi-user) system is one where a number of users are able to use the same system together. • Modern personal computers can allow multi user access i.e. more than one person can make use of the computer resources at the same time via a LAN. • The central processor deals with users in turn; clearly the more users, the slower the response time. • Generally, however, the processor is so fast that the response time at the most is a fraction of a second and the user feels they are being dealt with immediately. Multi-access or multi-user

  12. A batch processing system is where programs or dataare collected together in a batch and processed in one go. • Typically the processing of payrolls, electricity bills, invoices and daily transactions are dealt with this way. • This method of operation lends itself to jobs with similar inputs, processing and outputs where no human intervention is needed. • Jobs are stored in a queue until the computer is ready to deal with them. Often batch processed jobs are done overnight. Batch processing

  13. 1. Define the following terms • Interface • Main frame • Operating system 2. Explain how an operating system would use Multi-Tasking in order to provide you with an effective windows environment to work with 3. Give THREE examples of a situation where Real Time processing is needed Task

  14. Have a go at the Quiz by clicking on the image A Quiz

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