O level Computer Revision Plan for Week 1

This revision guide describes what you need to know about your O Level Computer Science 2210/0478 examination.

It will help you plan your revision programme and will explain what the examiners are looking for in the answers to the questions. It can also help you to revise by using the tick boxes in Section 3 “What you need to know” to check what you know and which topic areas of the syllabus you have covered.

A computer system

A computer system is one that is able to take a set of inputs, process them and create a set of outputs. This is done by a combination of hardware and software.

The diagram below shows you the idea of a computer system in its most basic form

The computer system has one or more inputs to provide data. This data is then processed in some way. The outcome of the processing is sent to an output or it may be stored until some event happens to cause it to be output.

For processing to take place, there needs to be a set of instructions of what needs to be done. This set of instructions is called a program.

This system is called a stored-program computer.

  

Input Devices

Two-dimensional scanners
2D scanner or an image scanner—often abbreviated to just scanner, is a device that optically scans images, printed text, handwriting, or an object, and converts it to a digital image. The image is converted into an electronic form which can be stored in a computer.
Commonly used in offices are variations of the desktop flatbed scanner where the document is placed on a glass window for scanning.

Modern scanners typically use a charge-coupled device (CCD) or a contact image sensor (CIS) as the image sensor

"A flatbed scanner is usually composed of a glass pane (or platen), under which there is a bright light (often xenon, LED or cold cathode fluorescent) which illuminates the pane, and a moving optical array in CCD scanning. CCD-type scanners typically contain three rows (arrays) of sensors with red, green, and blue filters."