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Page 1

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Processing Data

Page 2

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Representing Numbers
Recap on Binary Numbers
Binary digit (1 or 0)
­ known as a `bit', short for BInary digiT
­ bits generally grouped together in 8-bit bytes
­ a byte can hold 28 combinations of 0s and 1s
­ This means that, for example, 256 different
characters can be…

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Some of the ASCII codes
Char ASCII Char ASCII Char ASCII Char ASCII
space 0100000 8 0111000 P 1010000 h 1101000
! 0100001 9 0111001 Q 1010001 i 1101001
( 0101000 @ 1000000 X 1011000 p 1110000
) 0101001 A 1000001 Y 1011001 q 1110001
* 0101010 B 1000010 Z…

Page 4

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Real Numbers
Numbers with a decimal point are known as
real numbers
The system for holding numbers in this way
is not part of the course.
Be aware that if `numbers' are to be used in
calculations, they have to be held as
numbers and not as text.

Page 5

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Digitised Sound
Sound can be input using a number of devices
As with basic telephone line, sound is analogue (wave form)
Convert to digital form (i.e. a binary pattern) for storage and
processing
Hardware ­ sound card does conversion from analogue to
digital and vice versa.
Sampling rate ­ how…

Page 6

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Musical Instrument Digital Interface
MIDI is industry standard applied to:
­ Electronic musical instruments
­ Hardware, cables, connectors & data
MIDI interface allows computer to communicate:
­ Keyboards, drum pads, guitars etc.
MIDI data system stores all info. Necessary to synthesise
musical sounds.
Digitally stored data is very compact:
­…

Page 7

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Bit-Mapped Graphics
Screen is divided into a grid
­ Each square is called a pixel (picture element)
Higher Resolution has more squares
­ Standard used to be 640x480, is now 800x600 but rapidly
moving toward 1024x768 as standard
­ Monochrome only requires 1 bit in memory, (if 1, the pixel…

Page 8

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Bitmapped and Vector-based Graphics
Bitmapped images
­ are collections of pixels
­ Images created by setting colour and other attributes
for each pixel
­ the amount of memory required is dependent upon
the display adapter
­ Problems:
· May not look correct if transferred to another machine
with different adapter…

Page 9

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Bitmapped and Vector-based Graphics
Vector-based (or object-oriented) Graphics
­ Image is based on geometric data NOT graphic
data
­ A line defined by is endpoints, length, colour and
so on
· Used by CAD programs (or special graphics software)
to create the line on any screen regardless of its
resolution…

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