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Computer Science A level > Fundamentals of Data Representation > Flashcards

Fundamentals of Data Representation Flashcards

1
Q

What are natural numbers?

A

Natural numbers are a set of numbers that include all positive whole numbers and zero. They are used for counting items.
The symbol for natural numbers is ℕ.

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1
Q

What are integer numbers?

A

Integer numbers are a set of whole numbers, including positive numbers, negative numbers, and zero.
The symbol for integer numbers is ℤ.

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2
Q

What are rational numbers?

A

Rational numbers can have a fractional part and can be written as a fraction of one number over another.
The symbol for rational numbers is ℚ.

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3
Q

What are irrational numbers?

A

Irrational numbers cannot be written exactly as a fraction and include numbers like π, √2, and e.

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4
Q

What are real numbers?

A

Real numbers include all possible real-world quantities and encompass irrational numbers, rational numbers, integers, and natural numbers.
The symbol for real numbers is ℝ.

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5
Q

What are ordinal numbers used for?

A

Ordinal numbers are used to describe the numerical positions of objects in relation to others, such as 1st, 2nd, or 3rd.

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6
Q

What is a bit?

A

A bit is the fundamental unit of information that can take two values, 1 and 0.

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7
Q

What is a byte?

A

A byte is a collection of 8 bits.

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8
Q

What is a nybble?

A

A nybble is half a byte, consisting of 4 bits.

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9
Q

How is a bit denoted?

A

A bit is denoted with a lowercase “b”.

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10
Q

How is a byte denoted?

A

A byte is denoted with an uppercase “B”.

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11
Q

How many bits are in 2 bytes?

A

There are 16 bits in 2 bytes.
2 x 8 bits

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12
Q

How many bits are in 20 bytes?

A

There are 160 bits in 20 bytes.
20 x 8 bits

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13
Q

How many different values can be represented with a specified number of bits?

A

There are 2^n different values that can be represented with n bits

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14
Q

How many different values can be represented with 8 bits?

A

With 8 bits (1 byte), there are 256 different values that can be represented (2^8 = 256).

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15
Q

What is the value of 1 kilobyte (KB)?

A

1 kilobyte (KB) = 1000 bytes.

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16
Q

How do you calculate absolute error?

A

Absolute error is calculated by finding the difference between the given value and the actual value.

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17
Q

How do you calculate relative error?

A

Relative error is calculated by dividing the absolute error by the actual value.

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18
Q

What is the advantage of floating point representation over fixed point representation?

A

Floating point representation allows for a greater range of numbers with a given number of bits by utilizing an exponent, which can be positive or negative.

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19
Q

What is normalization in floating point numbers?

A

Normalization in floating point numbers ensures that the number starts with 01 (for positive numbers) or 10 (for negative numbers) in order to provide the maximum level of precision.

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20
Q

What is underflow?

A

Underflow occurs when very small numbers are to be represented, but there are not enough bits available to accurately represent them.

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21
Q

What is a character code?

A

A character code is a decimal digit used to represent a character in an information coding system.

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22
Q

How many bits are used in ASCII to represent different characters?

A

ASCII uses 7 bits to represent 128 (= 2^7) different characters

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23
Q

What are parity bits used for?

A

Parity bits are used for error checking in transmitted data.

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24
Q

How does majority voting work?

A

In majority voting, each bit of the data is transmitted multiple times, and the most commonly occurring value is considered correct.

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25
Q

What is a checksum?

A

A checksum is a value calculated based on the data being transmitted, which is added to the transmitted data for error detection.

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26
Q

What is a check digit?

A

A check digit is a single digit added to the transmitted data as a form of checksum to detect errors.

27
Q

What is the efficiency of parity bit, majority voting, checksum, and check digit for error detection and correction?

A
  • Parity bit: Can detect errors in transmission but can only correct errors if an odd number of bits are changed. It is very efficient.
  • Majority voting: Can detect and correct errors as long as the majority of bits remain unchanged. It is inefficient due to increased data volume.
  • Checksum: Can detect errors but cannot correct them. It is mostly efficient, depending on the complexity of the algorithm used.
  • Check digit: Can detect errors but cannot correct them. It is efficient as the algorithms used for calculating check digits are limited in complexity.
28
Q

What is an advantage of ASCII over Unicode?

A

ASCII requires fewer bits (7 bits) compared to Unicode, which allows for more efficient storage and transmission of data.

29
Q

What is an advantage of Unicode over ASCII?

A

Unicode can represent a much wider range of characters, including various languages, symbols, and emojis.

30
Q

What is an advantage of majority voting over parity voting?

A

Majority voting can not only detect errors but also correct them, whereas parity voting can only detect errors.

31
Q

What is a disadvantage of parity voting?

A

Parity voting can only detect errors if the number of changed bits is odd; it cannot detect errors if an even number of bits are changed.

32
Q

How does majority voting handle multiple bit errors?

A

Majority voting has the capability to correct errors even when the values of multiple bits have changed, providing robust error correction.

33
Q

How does parity voting handle multiple bit errors?

A

Parity voting fails to detect errors if an even number of bits have changed, making it less reliable than majority voting in such cases.

34
Q

What is the difference between analogue and digital data?

A

Analogue data is continuous and can take any value, while digital data is discrete and can only take specific values.

35
Q

How does an analogue signal differ from a digital signal?

A

An analogue signal can take any value and can change as frequently as required, while a digital signal must take one of a specified range of values and can only change at specified intervals.

36
Q

What devices are used for digital-to-analogue conversion and analogue-to-digital conversion?

A

A digital-to-analogue converter (DAC) is used for digital-to-analogue conversion, while an analogue-to-digital converter (ADC) is used for analogue-to-digital conversion.

37
Q

What is the process of sampling in analogue-to-digital conversion?

A

Sampling involves taking regular readings of an analogue signal at specific intervals to record its values digitally.

38
Q

How is an image represented in bitmap graphics?

A

In bitmap graphics, an image is broken down into pixels, and each pixel is assigned a binary value.

39
Q

What determines the resolution of an image?

A

Resolution can be expressed as the number of dots per square inch (dpi) or the number of pixels in the image.

40
Q

What is colour depth in bitmap graphics?

A

Colour depth refers to the number of bits assigned to each pixel in an image, determining the number of colours that can be represented.

41
Q

How do you calculate the storage required for a bitmap image?

A

Multiply the number of pixels (width × height) by the bit depth to calculate the storage required.

42
Q

What additional information can be included in a bitmap image file?

A

Bitmap image files may contain metadata, such as the image’s width, height, date created, and colour depth, in addition to the pixel data.

43
Q

How are images represented in vector graphics?

A

Vector graphics represent images using geometric objects and shapes, storing the properties of each shape in a list.

44
Q

What is the advantage of vector graphics when it comes to scaling images?

A

Vector graphics can be scaled without losing quality, unlike bitmapped graphics, which may result in blurriness or pixelation when enlarged.

45
Q

Which type of graphics is more suitable for storing photographs?

A

Bitmapped graphics are used for storing photographs.

46
Q

How does a computer represent sound digitally?

A

Computers represent sound as a sequence of discrete samples, each taking a digital value.

47
Q

What is the sampling rate in sound representation?

A

The sampling rate is the number of samples per second and is measured in Hertz.

48
Q

What does the sample resolution in sound representation refer to?

A

The sample resolution is the number of bits allocated to each sample and affects audio quality and file size.

49
Q

How can the size of a sound sample be calculated?

A

Multiply the duration of the sample in seconds by the sampling rate in Hertz and the sample resolution in bits.
(Sound Sample (fbs) = Sampling Rate (f) x Sample in bits (b) x duration of sample (s)

50
Q

What is the Nyquist theorem in sound representation?

A

The Nyquist theorem states that the sampling rate must be at least twice the frequency of the sound to accurately represent it.

51
Q

What is MIDI used for?

A

MIDI (Musical Instrument Digital Interface) is used with electronic musical instruments connected to computers to store sound as a series of event messages.

52
Q

What are the advantages of using MIDI over sampled recordings in music representation?

A

Advantages of MIDI include easy manipulation of music without quality loss, changing instruments, transposing notes, and altering note duration. MIDI files are also smaller in size and lossless.

53
Q

Why are files compressed?

A

Files are compressed to reduce their size, enabling faster transfer between storage devices or over the internet.

54
Q

What are the two categories of compression?

A

The two categories of compression are lossy compression and lossless compression.

55
Q

What is the difference between lossy and lossless compression?

A

Lossy compression results in some information loss, while lossless compression reduces file size without decreasing quality.

56
Q

What are two methods of lossless compression?

A

Two methods of lossless compression are run length encoding (RLE) and dictionary-based methods.

57
Q

Explain run length encoding (RLE).

A

RLE reduces file size by removing repeated information and replacing it with one occurrence of the repeated information followed by the number of times it is to be repeated.

58
Q

What are dictionary-based methods in compression?

A

In dictionary-based methods, a dictionary containing repeated data is appended to the file to reduce its size.

59
Q

Which type of data is most suitable for compression using run length encoding and dictionary-based methods?

A

Files that contain a lot of repeated data are most suitable for compression using these methods.

60
Q

What is encryption?

A

Encryption is the process of scrambling data to keep it secure during transmission, making it unreadable if intercepted.

61
Q

What is plaintext and ciphertext?

A

Unencrypted information is referred to as plaintext, while encrypted information is called ciphertext.

62
Q

What are Caesar ciphers?

A

Caesar ciphers encrypt information by replacing characters, either by shifting the alphabet or using substitution.

63
Q

What is the Vernam cipher?

A

The Vernam cipher is a one-time pad cipher that requires a random key at least as long as the plaintext, encrypting by applying a logical XOR operation.

64
Q

Is the Vernam cipher considered secure?

A

Yes, the Vernam cipher is considered completely secure and is the only cipher mathematically proven to be so.

65
Q

What is computational security in ciphers?

A

Ciphers other than the Vernam cipher are theoretically crackable but not within a reasonable timeframe given current computing power, relying on computational security.

Computer Science A level (9 decks)

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