1. 1 AQA ICT AS Level © Nelson Thornes 2008 Operating Systems What are they and why do we need them?

2. 2 AQA ICT AS Level © Nelson Thornes 2008 What is an operating system? When people use a computer, they usually want to do something using applications software, such as a word processor or even a computer game. Applications software will not run without systems software being installed. For example, operating system software makes all the electronic parts work together as a computer.

3. 3 AQA ICT AS Level © Nelson Thornes 2008 Functions of an operating system The operating system controls the system hardware. It is responsible for: booting up the system when the computer is first switched on managing memory during multi-tasking allocating processor time between tasks controlling where data is stored on disk communicating with input and output devices handling errors, system security, user and file permissions.

4. 4 AQA ICT AS Level © Nelson Thornes 2008 Communication The operating system needs to: interface with peripherals such as a mouse or printer handle interrupts – signals that need an immediate response, such as a mouse click to stop a file printing. Right! What do I have to send?

5. 5 AQA ICT AS Level © Nelson Thornes 2008 Handling storage The operating system organises the storage and retrieval of data files from backing storage such as the hard drive. It keeps a directory of where the files are stored on disk. It keeps track of the free space on the drive so that files can be stored efficiently for faster retrieval. Now where did I put that?

6. 6 AQA ICT AS Level © Nelson Thornes 2008 Memory management Ok, what shall I do next? While computers seem to be able to multitask, a single processor can only do one thing at a time. Dual and quad core processors behave as if the computer has more than one processor. The operating system allocates processing time and memory to the various tasks that need to be carried out.

7. 7 AQA ICT AS Level © Nelson Thornes 2008 Types of interface The operating system also provides the user different interfaces, such as: Graphical User Interface Command Line Interface Menu Driven Interface

8. 8 AQA ICT AS Level © Nelson Thornes 2008 Utilities The operating system may have some utilities such as file management software already built in. Other systems software, such as anti-virus software and firewalls, may need to be purchased separately.

9. 9 AQA ICT AS Level © Nelson Thornes 2008 Application Software

10. 10 AQA ICT AS Level © Nelson Thornes 2008 Application software Application software carries out the tasks the user wants to perform. When choosing the application you need to consider: What are the functions of the available software? What are the end user requirements? What is the experience and skill level of the end user? Is the existing data transferable to the new software? Is it compatible with other software currently used? Will the benefits of the new software be worth the financial cost involved? Why choose a particular package?

11. 11 AQA ICT AS Level © Nelson Thornes 2008 Desktop publishing and word processing Desktop publishingWord processing Offers a wide range of templates for both home and office use. Offers templates and wizards for standard documents used by businesses. Objects contained in frames allows more freedom when choosing layouts. Layout tools focus on text, including index and table of contents. Offers a limited selection of graphics and drawing tools. Special features to track changes on a document owned by multiple users.

12. 12 AQA ICT AS Level © Nelson Thornes 2008 Vector and bitmap images Vector imagesBitmap images The shape of an object is plotted mathematically. The image is made up of pixels, a series of small dots or squares. When you resize a vector image the quality remains the same. When you resize a bitmap image the pixels get bigger reducing quality and often having jagged edges. Some packages allow 2D drawing to be converted to 3D wire frames. The fills on bitmap images allow a more realistic texture to be created. Often used for clip art, diagrams and computer aided design. Often used for freehand art and photographs.

13. 13 AQA ICT AS Level © Nelson Thornes 2008 Spreadsheet and database management software Database management software A flatfile database is made up of a single table. A relational database links two or more tables. Databases are mainly used for text but they support many other data types. This software offers features such as validation, sorts, queries, forms and reports.

14. 14 AQA ICT AS Level © Nelson Thornes 2008 Spreadsheet software Spreadsheets can be used to make informed decisions through modelling. Spreadsheets are mainly used to analyse and record numbers but do support other data types. Spreadsheets can perform advanced calculations using a variety of mathematical functions. Most packages offer limited database functions. Spreadsheet and database management software

15. 15 AQA ICT AS Level © Nelson Thornes 2008 Moving images Video editing software Animation software Allows the user to draw only the start and end position of object and the computer draws the frames in between. The playback speed can be adjusted to make the objects run faster or slower. The number of frames can be adjusted to make the file size smaller. However more frames make the animation smoother. Sections of videos can be removed or the user can cut a paste sections just like text in a word processor. Sound files and music can be added to run alongside the video files. Video files have large file sizes, they can be compressed but this makes the video lose some quality.

16. 16 AQA ICT AS Level © Nelson Thornes 2008 Sound and music editing Sound editing software can…. change the pitch and the volume of sound change the pattern of sound waves cut and paste sections of waves combine several tracks of sound to be played together. Music composition software can…. be used to drag notes directly onto a stave transcribe music played on a keyboard connected to the computer play a composition in the sound of many different instruments transpose music into different keys.

17. 17 AQA ICT AS Level © Nelson Thornes 2008 Multimedia Multimedia software does not concentrate on one type of data, it combines them all. Examples of multimedia software include presentation and web authoring software. Multimedia software offers a unique opportunity to present material in a way that is accessible to a wide range of users with different needs. Presentations can be made interactive, where the user controls how they move through them.