Saturday, 26 December 2015
Thursday, 24 December 2015
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."
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.
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