3.3 Data Representation Flashcards

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1
Q

What is binary?

A

A number system that uses 1s and 0s

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2
Q

Why is Binary used?

A

Because it has two states (1 and 0) which can represent on/off, true/false, open/closed for example

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3
Q

What is binary used for in a computer?

A

Computers are based on circuits with switches that are either open or closed. The binary number system can therefore be used to change the switches because it also has two states of 1 and 0

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4
Q

What is the Most Significant Bit (MSB)?

A

Bit furthest to the left with the largest place value

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5
Q

What is the Least Significant Bit (LSB)

A

Bit furthest to the right with the lowest place value

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6
Q

How to work out the number of binary representations?

A

2^n

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7
Q

How to work out the largest number in a certain number of bits?

A

2^n - 1
n is the number of bits

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8
Q

What are the different sizes of storage?

A

bit (b) = 0 or 1 or 1/8 byte
nibble = 4 bits or 1/2 byte
byte (B) = 8 bits
kilobyte (KB) = 1 000 bytes
megabyte (MB) = 1 000 000 bytes
gigabyte (GB) = 1 000 000 000 bytes
terabyte (TB) = 1 000 000 000 000 bytes

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9
Q

What is an overflow error?

A

The result of the addition is too large to store in 8 bits i.e the result is greater than 255

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10
Q

How do you convert from hexadecimal to denary?

A

16 |1 |
3 |B |
(3 x 16)| + 11 |= 59

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11
Q

How do you convert from denary to hexadecimal?

A

229 / 16 = 14 (E) remainder 5 = E5

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12
Q

Who uses hexadecimal?

A

Humans - programmers, Computer Scientists
Computers ALWAYS use binary

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13
Q

Why use hexadecimal?

A
  • Easier to remember a hex number than a binary number
    -Because it is a more compact form -
    four binary digits are represented with
    a single hex value
    -Therefore it is less likely that
    errors are made
  • It is easy to convert between hex and binary
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14
Q

What are the effects of shifts?

A

Direction| Places | Outcome

Left | 1 | x 2
Left | 2 | x 4
Left | 3 | x 8
Left | 4 | x 16

Right | 1 | / 2
Right | 2 | / 4
Right | 3 | / 8
Right | 4 | / 16

LEFT = multiply
RIGHT = divide

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15
Q

What are the effects of a right shift?

A

Loss of accuracy as bits may be lost

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16
Q

What are the two main character sets used today?

A

ASCII
Unicode

17
Q

What is a pixel?

A

The smallest identifiable part of an image

18
Q

Calculating image file size

A

in bits
= width x height x colour depth
in bytes
= width x height x colour depth / 8

19
Q

What is metadata?

A

Data in data - information other than the actual image data is also stored with a file

20
Q

What is included in the metadata?

A

Colour Depth
Height and width of image in pixels
Date created
Author
GPS - where it was taken

21
Q

Why is metadata necessary?

A

Allows the binary data to be correctly interpreted

22
Q

How is a computer able to store sound?

A

The analogue wave is digitised by repeatedly measuring and recording the sound wave

23
Q

Difference between analogue and digital waves

A

analogue - continuous waves
digital - signals are discrete

24
Q

What does an Analogue to Digital Converter do?

A

Takes an analogue sound waves as an input and converts it to a digital signal.
Done by a Sound card

25
Q

What does a Digital to Analogue Converter do?

A

Takes the digital signal and converts it to an analogue sound wave as an output.
Done by a Sound card

26
Q

What is a sound sample?

A

A sound sample is a measurement of amplitude (height) of a sound wave at a given time

27
Q

What is the sampling rate?

A

The sampling rate is the number of samples taken per second.
It is measured in hertz (Hz):
- 1Hz = 1 sample per second

28
Q

What is the sample resolution (or bit depth)?

A

The number of bits used to record each measurement is known as the sample resolution or bit depth

29
Q

What is the formula for calculating sound file sizes?

A

File size (bits) = sampling rate (Hz) × resolution × duration (seconds)

30
Q

What frequency can humans hear sounds?

A

20 - 20,000 Hz

31
Q

What is Lossy compression?

A

Permanently removes parts of the file
The lost piece of data can never be restored

32
Q

What is Lossless compression

A

Reduces the file size when compressed but does not lose any information

33
Q

What is compression?

A

Compression is the name given to the algorithms which reduce file size.

34
Q

What is decompression?

A

Decompression is the process where compressed data is restored to its original format

35
Q

What is Run Length Encoding (RLE)?

A

RLE uses frequency/data pairs to encode each run length of the same coloured pixel

36
Q

What does Huffman coding analyse?

A

Frequency with which characters in a body of text are used

37
Q

Benefits of compression

(you don’t need to know them all)

A

-Faster transmission time-
Smaller file size = fewer bits = faster transmission time

-Reduces network traffic-
Smaller fie size = less network traffic = fewer packet collisions

-Video Streaming-
Data can be sent as fast as it can be played

-Detailed webpages-
More extensive content can be displayed on webpages as it will download quicker

-Reduced storage space-
Files do not take up as much space on the disk/server