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Computer Systems

Computer Systems. Nat 4/5 Computing Science Operating Systems. Lesson Aims. By the end of this lesson: All pupils will be able to: Describe what an operating system is Describe the functions of an operating system National 5 pupils will be able to: Describe what an application program is

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Computer Systems

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  1. Computer Systems Nat 4/5 Computing Science Operating Systems

  2. Lesson Aims • By the end of this lesson: • All pupils will be able to: • Describe what an operating system is • Describe the functions of an operating system • National 5 pupils will be able to: • Describe what an application program is • Describe a web browser • Describe some utility programs

  3. Nat 4/5 Types of software • There are two main types of software: • Applications • These are types of software that perform a particular task such as word processing or desktop publishing • Operating Systems • This software manages the hardware and the software that is being used

  4. Nat 5 Applications Software • Application software are programs that are designed to do a particular task. • For example the Microsoft Word Even games are application programs.

  5. Nat 4/5 Operating Systems • An operating system is a piece of software that controls the operation of the hardware and the running of other software. • Two of the more popular operating systems used at present are • Microsoft® Windows • Apple® OSX.

  6. Nat 4/5 Which operating system?Does it matter? • Imagine you are writing an app for a smartphone • Which operating system do you write it for? • IOS®, Android ® or Windows ® ? • Why do you need to bear this in mind? • If I buy Office 2010 for Windows – can I install it on a Mac?

  7. Nat 5 Functions of an operating system • User Interface • Input and output • Memory Management • File management • Error reporting • Kernal

  8. Nat 5 Functions: User Interface • This lets the user give commands and see the effect of their commands • Graphical User Interface – icons • Command line interface - lets the user type commands

  9. Nat 5 Functions - Input Output • Controls the sending and receiving of data to and from peripherals

  10. Nat 5 Functions - Memory Management • Controls which locations in RAM each program is loaded into

  11. Nat 5 Functions - Memory Management • Allocates space in memory for programs & data • Allows multi-tasking – more than 1 program in memory at a time that user switches between • Prevents operating system in RAM being overwritten by user’s programs and data – memory protection

  12. Nat 5 Functions - Memory Management OS decides which locations a program will be loaded into OS ensures that a program doesn’t accidentally use the memory allocated to another program When a program does try to use memory set aside for the operating system, or another program, it usually crashes.

  13. Nat 5 Functions - File Management • Decides where files are saved on backing storageand finds files when they to be loaded

  14. Functions - File Management • Makes efficient use of backing storage • Updates a catalogue of files on outer tracks of disk that stores details of file’s address on disk • adds file name and location on disk when saving • Removes name when deleting • Looks up catalogue when loading a file to find the file on disk • Passes details to I/O system to load file

  15. Functions - File Management Directory Sub-directory Organises files in hierarchical filing system Allows a logical arrangement of files Same filename can be used in different directories Unique pathname to identify file File

  16. Nat 4/5 Functions - Error Reporting • Providing useful feedback to users when errors occur

  17. Summary The Operating System (OS) of a computer is a program which manages the hardware and the running of other software on a computer system. The standard functionsof an OS are: • User interface • Input/Output • File Management • Memory management • Error Reporting An application program is a piece of software that performs a particular task such as games, word processor. Nat 4/5

  18. Pupil Task Pick three different operating systems and find the following: • Its latest version (name or Number) • Three features of the OS • One recent news article about the OS (recent being in the last year)

  19. Utility programs • Perform everyday tasks • May be part of the operating system • May be separate programs • Examples:- • Virus checker – detects and removes viruses • Defragmenter – tidies up hard disk • Backup – creates backup copy of files • Converters, compressors & expanders • Installers/uninstallers – copy program to hard disk or remove it • Printer drivers – enable the computer to send the correct signals to the printer • Email filter & web filters

  20. Virus checker • Virus – rogue program that copies itself by:- • being carried on a memory stick • through a network by e-mail • Computer Misuse Act(1990) makes distributing a virus illegal • Virus checking software detects then removes the virus • Updates downloaded to ensure that new virus can be dealt with

  21. Web browsers • Internet Explorer • MozillaFirefox • Safari • Google Chrome • Program that understands HTML and displays web pages

  22. Questions • Name 3 utility programs that you have used • Describe the function of a web browser • State 5 functions of an operating system

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