# Computer Science - Representing data

• Created by: becky.65
• Created on: 20-05-15 11:59
How are all the symbols on a computer displayed?
By a code
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What are the codes stored in?
Binary
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What is the character set for the computer?
The list of codes and matching characters
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How many bits does ASCII use?
7 bits or extended ASCII uses 8 bits
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How many bits does Unicode use?
16 or 32 bits
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What does Unicode provide
A character set for a computer that includes a wide range of specialist symbols
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Since Unicode keeps the same assignment of codes for the original ASCII codes so what could ASCII be considered as now?
A subset of Unicode
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How are images stored on a computer
In binary
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How is the computer able to work out how to turn binary values into the image?
The file with the binary data contains metadata
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What is a pixel?
One 'dot' in the image
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What does the number of bits we use for a pixel determine?
How many colours each dot can represent
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What two things need to get greater for more bits needed to store the data
The more bits per pixel and the greater the colour depth
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What is 16bpp called?
High colour
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What is 24bpp called?
True colour
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What is the resolution?
The number of pixels per unit
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What is a bitmapped image?
An image built up from pixels
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What happens when a bitmapped image is displayed enlarged on a screen?
The actual image size does not change, the dots just get bigger and the image becomes pixelated
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Why are sound files described by metadata?
To make sure the computer can interpret the data accurately
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What does the data stored include?
The audio codec and the sample rate
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What form is sound in?
Analogue form
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Since it is in analogue form, what needs to happen for sound to be transferred to a computer?
It needs to be digitally sampled
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What is the sample interval?
Often used to describe the sample rate and is the time between samples being taken
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So the higher the sample interval the...?
Lower the sample rate
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What happens when sound is sampled at a low rate?
Very few samples are taken, there is a poor match between the original sound and the sampled sound and a small file size is required
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What happens when sound is sampled at a higher rate?
Many more samples are taken, there is a good match between the original sound and the sampled sound and a large file size is required
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What is the bit rate?
The amount of space to to store each second of the sample
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What does a higher bit rate mean?
More accurate sampling at each point which gives better quality and more data needs to be stored which needs a larger file size
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What does the CPU when it fetches an instruction?
It decodes it in order to find out what to do next
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What are the two parts of the instruction
Operator, which is the instruction part ad the operand which is the data part
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What does the operator binary code represent?
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What does the operand represent?
The data that the operator uses
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What is the accumulator?
A special register in the CPU used to store the results of any calculation
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How does a computer tell the difference between data and instructions?
It cannot tell the difference between them and simply deals with what it finds according to what us expects to find
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## Other cards in this set

### Card 2

#### Front

What are the codes stored in?

Binary

### Card 3

#### Front

What is the character set for the computer?

### Card 4

#### Front

How many bits does ASCII use?

### Card 5

#### Front

How many bits does Unicode use?