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Operating Systems By the end of this session, you will know: What an Operating System is. The functions it performs. Operating Systems What is it? An OS is a set of programs that controls how the hardware of a computer works… It is the means of communication between the user and the computer, deals with the loading and running of application programs and manages the transfer of data and files to and from the peripheral devices. Operating Systems User Applications Software Operating System Computer Hardware The OS acts like a bridge between the applications software and the computer hardware. Users need applications software to carry out tasks, the software needs the operating system in order to communicate with the hardware. Operating Systems Functions: • Accepts data from input devices and transfers it to the computer’s memory. • Makes sure any output is sent to the correct output device. • Manages the transfer of data between the computer’s memory and backing storage devices. Operating Systems Functions: • Allocates memory space to programs and data. • Loads applications software into memory and controls the running of them. • Deals with any errors that occur when a program is being run and informs the user. Operating Systems Functions: • Provides a human computer interface for the user • Provides special facilities for multiprogramming. • Manages system security by restricting access to prevent unauthorised access to the system. …So, the OS is quite important! Examples of operating systems There are a number of operating systems that you could use on your computer. The one that you are most likely to be familiar with is one of the Microsoft Windows operating systems. Almost all personal computers are loaded with Windows before you purchase them and most schools use a network version. If you use an Apple Mac computer then you will be familiar with Apple's unique operating system, Mac OS. Many people find this far easier and more intuitive than Microsoft's Windows versions. Linux is an alternative operating system for most computers. It has the advantage of being free of charge. This is because it is 'open source' software. Operating Systems Question! • Transferring data to a printer? Which 3 of the following is an OS responsible for? • Allocating storage space on a disk? • Positioning text in a word processing document? • Finding a database record? • Accepting keyboard input? • Adding colour to a drawing on screen? SELF ASSESSMENT 1. One of the roles of an operating system is to allocate - 2. A well known brand of operating system – 3. Which operating system would a Mainframe computer use? Windows,Mac-OS,Unix,Office 4. Which operating system would a desktop PC most often use? Windows,Unix,Office,Linux 5. Software and hardware cannot communicate without an ____________ Rubrics Q.Nos Answers Marks 1. Resources (1) Correct (0) wrong 2. Windows Correct wrong 3. Unix Correct wrong 4. Windows Correct wrong 5. Operating System Correct wrong RECAP Tasks of the operating system Next Class Will be studying about : – Multiprogramming – Multitasking – Multiuser Operating System Learning Onjectives: 1) Recap of Previous Class: - Definition of OS, Tasks, Examples. 2) What are Multiprogramming, Multitasking, Multiuser? Operating Systems Multiprogramming: A multiprogramming OS holds more than one program in memory. There are 2 Types of Multiprogramming OS you need to know : Multitasking and Multiuser Operating Systems Multitasking: A Multitasking OS allows two or more programs to run at the same time. …It’s like having MS Word, iTunes and Solitaire open on your computer at the same time! Operating Systems Multitasking: Multitasking is allowed as the OS swaps each program in and out of memory in turn when needed. The program not being used is temporarily stored on the backing storage until needed again. Operating Systems Multitasking: CPU Backing Store Program A (Not used) Program C (Being used) Program B (Just used) Operating Systems Multiuser: A Multiuser OS allows many different users at different terminals (in a network) to share the processing time on a central computer. Operating Systems Multiuser: This is allowed as the OS switches quickly between the terminals and giving each one a small amount of processing time on the central computer (called a time slice). Operating Systems Multiuser: Terminal 2 Terminal 1 Central Computer OS Terminal 4 Terminal 3 Processing power will be given in a ‘round robin’ way! PEER ASSESSMENT 1. ____________ is allowed as the OS swaps each program in and out of memory in turn when needed. 2. The program not being used is temporarily stored on the __________until needed again. 3. An operating system that can be used by many people at once. 4. An operating system that is designed for use by one person at a time 5. There are 2 Types of Multiprogramming OS ____________ & ________________ Rubrics Q.Nos Answers 1. Multitasking Marks (1) Correct 2. Backing storage Correct wrong 3. Multiuser Correct wrong 4. Singleuser Correct wrong 5. Multitasking Multiuser Both Correct – 1 If one correct - ½ Both wrong (0) wrong