comp sci unit 3

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  • Created by: RishiMcA
  • Created on: 28-11-23 14:24
binary units
1 bit = a single 0 or 1 (b represents bit)
1 byte = 8 bits = 1 character of text (B represents byte)
(A nibble = 4 bits or half a byte)
1 kB (kilobyte) = 1000 bytes
1 MB (megabyte) = 1000 kB or 1000x1000 bytes
1 GB (gigabyte) = 1000 MB
1 TB (terabyte) =
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2 main character sets
There are two major character sets in use today:
ASCII
Unicode
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hexadecimal
number / 16
remainder
18
18/16 = 1
remained 2
so answer is 12
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unicode
character set for every alphabet
16 bit or 32 bit
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asciii
character set just for latin alphabet eg.enlgish
7 bit (8bit in extended)
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lossy compression
Lossy compression permanently loses some data but can compress smaller
eg. a video
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lossless compression
dont loose any data but can't compress as small
eg. text
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5 image file types
BMP
JPG
GIF
PNG
TIFF
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What are pixels and how do they work
Bitmap images are made up of PICture ELement
or pixels
A pixel is the smallest
identifiable area of an
image
Each pixel is a single
colour and is given a
binary value which
represents that colour
e.g. 111100000000
might equal red
A pixel’s colour
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Image resolution
Resolution is the concentration of pixels within a specific area
The area is defined by the image width and height in pixels e.g. 1920 × 1080
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colour / bit depth
8 bits per pixel = 28 = 256 colours
16 bits per pixel = 216 = 65,536 colours
24 bits per pixel = 224 = 16,777,216 colours
More bits per pixel = more colour combinations
bit depth = 3 then 2 ** 3 = 8
8 colours
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image file size
A bitmap image file size will be calculated by the following formula:
Size in bits = Width × Height × Colour depth
Size in bytes = Width × Height × Colour depth / 8
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Read
A bitmap graphic is made up of individual pixels
Each pixel is represented in binary
The number of bits per pixel determines the number of available colours for an image
Image metadata holds data about the image, such as colour depth, resolution, date cr
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sample resolution
A sound sample is a measurement of amplitude of a sound wave at a given time
Sound is sampled
using a
sample resolution
(bit depth)
and sampling rate
The sample
resolution
determines how
closely the wave
is sampled on
the y-axis
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sampling rate
The sampling rate is the number of samples taken
per second
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sample reoslution
The number of bits used to record each measurement is known as the sample resolution or bit depth
measured in hertz
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sample rate
The frequency or sample rate per second affects the level of detail in the digital representation
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calculation file size for sound
File size (bits) = sampling rate × resolution × duration
6 samples per second × 4-bit resolution × 3 seconds
= 72 bits / 8 = 9 bytes
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Other cards in this set

Card 2

Front

2 main character sets

Back

There are two major character sets in use today:
ASCII
Unicode

Card 3

Front

hexadecimal

Back

Preview of the front of card 3

Card 4

Front

unicode

Back

Preview of the front of card 4

Card 5

Front

asciii

Back

Preview of the front of card 5
View more cards

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