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Computer Science > Fundamentals of Data Representation > Flashcards

Fundamentals of Data Representation Flashcards

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1
Q

What is a natural number? (N)

A

A positive whole number used for counting and ordering.
Eg. 1,2,3,4

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2
Q

What is an integer? (Z)

A

A positive or negative whole number.

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3
Q

What is a relational number?(Q)

A

Any number that can be expressed as a fraction, with the numerator and denominator as whole numbers.

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4
Q

What is an irrational number?

A

A number that can’t be expressed as a fraction.
Eg. Root 2, pi

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5
Q

What is a real number?(R)

A

Any positive or negative value.
Used for measurements.

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6
Q

What is an ordinal number?

A

A number used to describe the numerical position of an object.
Eg. Second, fourth

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7
Q

What is a cardinal number?

A

A number used to describe a quantity.
Eg. One car, three dogs

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8
Q

What are the three number bases?

A

Base 2 - Binary - 0’s and 1’s
Base 10 -Denary - 0 -> 9
Base 16 - Hexadecimal - 0 -> 9 , A=10 -> F=15

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9
Q

What are the units of data in ascending order?

A

Bit x4
Nibble x2
Byte x1000
Kilobyte x1000
Megabyte x1000
Gigabyte x1000
Terabyte x1000
Petabyte x1000

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10
Q

What is a bit?

A

The smallest unit of data that can be processed by a computer.

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11
Q

What is the difference between a kilobyte and a kikibyte?

A

1 kilobyte = 1000 bytes
1 kikibyte - 1024 bytes

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12
Q

What is the difference between a signed and unsigned binary number?

A

Unsigned binary always has a positive value.
Signed binary could have either a positive or negative value.

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13
Q

How do you subtract 2 numbers using two’s complement?

A

1) Make the number being subtracted negative.
2) Do bitwise ADD on the two numbers.

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14
Q

How do you convert a positive number to a negative number?

A

1) Find the positive binary value
2) Flip the bits
3) Add binary value one

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15
Q

What is a parity bit?

A

A bit added to data to evaluate whether the data should be accepted or not.

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16
Q

What is majority voting?

A

A method of repeatedly sending the same bit multiple times, then the computer accepts the bit in majority.

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17
Q

What are the advantages of a parity bit?

A

Simple to implement
Low overhead

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18
Q

What are the disadvantages of parity bits?

A

Low reliability
No error correction

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19
Q

What are the advantages of majority voting

A

Reliable
Can detect and correct multiple-bit errors.

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20
Q

What are the disadvantages of majority voting

A

High overhead
Inefficient

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21
Q

What are check digits?

A

An additional digit at the end of a string of numbers designed to catch mistakes.

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22
Q

How do you calculate the check digit for ISBN-10?

A

Multiply by 10 then 9 then 8 ….
MOD 11
11 - ANS = check digit

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23
Q

How do you calculate the check digit for ISBN-13?

A

Multiply by 1 then 3 then 1 then 3…..
MOD 10
10 - ANS = check digit

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24
Q

What is a pixel?

A

The smallest element of an image.

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25
Q

What is a bitmap?

A

A map of where pixels should go.

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26
Q

What is the colour-depth?

A

The amount of bits needed to store all the colours for an image.

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27
Q

How do you calculate the number of colours?

A

2^colour-depth

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28
Q

What are true colour images?

A

24-but colour-depth images.

29
Q

What is metadata?

A

Data about data.

30
Q

What are examples of metadata?

A

Filename
Dimensions
Resolution

31
Q

What is resolution?

A

The number of pixels in an image
width x height

32
Q

What is the formula for the number of bits in an image?

A

resolution x colour-depth

33
Q

What are vector images?

A

An image made up of objects and co-ordinates.

34
Q

What are the advantages of vector images?

A

Never becomes pixelated
Smaller file size

35
Q

What is a JPEG image?

A

A data format for lossy compressed photos.

36
Q

What is a GIF image?

A

A data format for basic images that appear mainly on the internet. (8-bit)

37
Q

What is a BMP image?

A

An uncompressed file format for high quality images.

38
Q

What is a PNG image?

A

A lossless compressed file format that can handle transparent backgrounds.

39
Q

What is a SVG image?

A

A web friendly vector file format.

40
Q

What are raster graphics?

A

Using a bitmap to store images.

41
Q

What is the difference between analogue and digital sound?

A

Analogue sound is infinite sound waves that travel through the air.
Digital sound is discrete values stored in binary form.

42
Q

How does an Analogue to Digital Converter (ADC) work?

A

Records samples at regular intervals
Measure the amplitude of each sample
Assigns each sample a binary value

43
Q

What is a MIDI?

A

A set of protocols that allow digital instruments to communicate.

44
Q

Give examples on what a MIDI stores?

A

The note, how long the note is, the frequency of the not, how loud the note is. etc.

45
Q

What are the advantages of a MIDI?

A

Small file size
High quality reproduction as no background noise etc.
Easy to edit

46
Q

What is the sample rate?

A

How often you record the amplitude of a wave.

47
Q

What is the sample resolution?

A

The number of graduations of amplitude that are represented. (Number of bits)

48
Q

What is the formula for the sample size of a sound?

A

sample rate x sample resolution x length of recording (seconds)

49
Q

What is the Nyquist theorem?

A

The frequency stored should be double the rate of the highest frequency for the best quality of sound.

50
Q

What is compression?

A

The process of reducing a files size, allowing for faster transmission.

51
Q

What is lossless compression?

A

Compression of a file, where the original data can be reproduced without any loss.

52
Q

When is lossless compression used?

A

When the quality of the original file needs to be maintained.

53
Q

What is run-length-encoding?

A

A method of lossless compression where repeated data is grouped together to reduce file size.

54
Q

What is dictionary-based-encoding?

A

The lossless compression of text files buy storing common strings of characters.

55
Q

What is a disadvantages of dictionary-based-encoding?

A

The dictionary may become longer than text itself.

56
Q

What is lossy compression?

A

When unnecessary data is removed, where the original data can never be restored.

57
Q

When is lossy compression used?

A

When quality isn’t necessary.

58
Q

What can lossy compression not be used on?

A

Text files
Executable software

59
Q

What is encryption?

A

The process of scrambling the contents of a file to render it unreadable by a third party.

60
Q

What is plaintext?

A

Data that can be read by humans.

61
Q

What is ciphertext?

A

Encrypted data.

62
Q

What is decryption?

A

The process of deciphering encrypted data.

63
Q

What is the Caesar cipher?

A

When the alphabet is offset by a fixed number to encrypt it.

64
Q

How can the Caesar cipher be improved?

A

Polyalphabetic (use multiple alphabets)
Add keywords to the start of a message.

65
Q

What are the disadvantages of the Caesar cipher?

A

Easy to crack as there are only 25 possible keys and certain letters are used more frequently than others.

66
Q

What is the Vernam cipher?

A

It uses a one-time key pad, which is a unique key that is only used once to encrypt and decrypt a message.

67
Q

How do you make a Vernam cipher?

A

Plaintext XOR one-time key pad

68
Q

What are the advantages of the Vernam cipher?

A

If the key is completely random and only used once it is mathematically impossible to crack the code.

Computer Science (8 decks)

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