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Computer Science IGCSE > 1. Data Representation > Flashcards

1. Data Representation Flashcards

1
Q

Why does data have to be converted to binary to be processed by a computer?

A

Computers are built using switches that can either be on or off, which fits the binary number system (1/0)

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2
Q

Define binary data

A

Binary data is data represented using the binary number system, consisting of only two digits: 1 and 0

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3
Q

Why do computers use binary?

A

Computers are built using circuits and transistors. The circuits only need to check for states:

On/off
True/False
North/south
1/0

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4
Q

Define binary number system

A

A base-2 number system that represents number using only two digits: 0 and 1

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5
Q

What is an example of binary representation in secondary storage devices?

A

Magnetic hard drives, where North and South polarity represent 1 and 0

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6
Q

What is the advantage of processing data in binary format for computers?

A

Allows computers to perform complex calculations, store vast amounts of data efficiently, and operate at incredible speeds.

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7
Q

What is denary

A

A base-10 number system made up of 10 digits (0-9) where each digit has a weight factor of 10 raised to a power

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8
Q

What is hexadecimal?

A

Hexadecimal is a base-16 number system made up of 16 digits, including 10 numbers (0-9) and 6 letters (A-F)

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9
Q

How many unique values can one hexadecimal digit represent?

A

One hexadecimal digit can represent 16 unique values (0-F)

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10
Q

What is a binary digit called?

A

A bit

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11
Q

What is the largest decimal number that can be represented by 8 bits in binary

A

255 (11111111 in binary)

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12
Q

How many bits does one hexadecimal digit represent?

A

4 bits (half a byte or one nibble)

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13
Q

Define nibble

A

4 bits of binary data or half a byte

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14
Q

What is the non-mathematical method for converting denary to hexadecimal?

A

Convert denary to binary
Split into nibbles
Then convert each nibble to hexadecimal

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15
Q

What is the non-mathematical method for converting hexadecimal to denary?

A

Convert each hexadecimal digit to 4-bit binary
Join the 2 nibbles together
Convert binary to denary

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16
Q

Define byte

A

A unit of digital information that consists of 8 bits

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17
Q

Why is hexadecimal preferred when working with large values in Computer Science?

A

Hexadecimal is preferred because it takes fewer digits to represent a given value than binary, making it easier to read and less prone to errors when copying

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18
Q

What are three common uses of hexadecimal in computing?

A

MAC addresses
Colour codes
URL encoding

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19
Q

Define overflow error

A

When the result of a binary addition exceeds the available bits

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20
Q

Define binary shift

A

How a computer system performs basic multiplication and division by moving binary digits left or right a set number of times

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21
Q

What does a left shift do?

A

A left shift multiplies a binary number by 2

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22
Q

What does a right shift do?

A

Divides a binary number by 2

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23
Q

Define underflow error.

A

When a result is too small to be represented in the available storage space

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24
Q

Define two’s complement

A

A method of using signed binary values to represent negative numbers, where the leftmost bit is designated as the most significant bit (MSB)

25
Q

In 8-bit two’s complement, what is the value of the leftmost column?

A

-128

26
Q

Define character set

A

A defined list of characters that can be understood by a computer, where each character is given a unique binary code

27
Q

What is ASCII?

A

A character set that uses 7 bits allowing it represent a maximum of 128 characters

28
Q

What is the definition of extended ASCII?

A

A character set that uses 8 bits allowing it to represent 256 characters

29
Q

Define UNICODE

A

A character set that uses a minimum of 16 bits, allowing it to represent a minimum of 65,356 characters from all major languages around the world

30
Q

What does character encoding mean?

A

The process of assigning a unique binary code to each character in a character set.

31
Q

Define sampling

A

The process of measuring and capturing values of an analogue signal at regular intervals.

32
Q

What is an analogue signal?

A

A continuous signal that can only take on any value within a range, such as a sound wave

33
Q

What does Analogue to Digital conversion (A2D) mean?

A

The process of converting an analogue signal, such as sound, into a digital form that a computer can understand

34
Q

Define sample rate.

A

The amount of samples taken per second of an analogue signal, measured in Hertz

35
Q

Define sample resolution

A

The number of bits stored per sample of the sound

36
Q

Define duration

A

The length of time that something lasts in the context of sound, it refers to the length of the recorded audio

37
Q

Define bitmap

A

An image made up of squares called pixels, where each pixel is stored as a binary code

38
Q

What is a pixel?

A

The smallest element of a bitmap image

39
Q

Define resolution

A

The total amount of pixels that make up a bitmap image, calculated by multiplying the height and width of the image

40
Q

What does colour depth mean?

A

The number of bits stored per pixel in a bitmap image

41
Q

State the equation in terms of X for the maximum number of colours in an image with colour depth X

A

2* (2 to the power colour depth)

42
Q

How many bits are in a byte

A

8

43
Q

How many bits are in a Kibibyte?

A

1024 bytes (2^10 bytes)

44
Q

What is the difference between a megabyte and mebibyte?

A

A megabyte is 1000² bytes, while a mebibyte is 1024² bytes

45
Q

How do you convert bytes to bits?

A

To convert from bytes to bits, multiply by 8

46
Q

What is a Tebibyte?

A

2⁴⁰ bytes

47
Q

What is the symbol for Mebibyte?

A

MiB

48
Q

How do you convert from kibibytes to bytes

A

Multiply by 1024

49
Q

What is the formula for calculating the size of a bitmap image?

A

image width × image height × colour depth

50
Q

What is the formula for calculating the size of a sound file?

A

Sample rate × duration × sample resolution

51
Q

How do you convert file size from bytes to kibibytes?

A

Divide by 1024

52
Q

Define compression

A

Reducing the size of a file so that it takes up less space by secondary storage

53
Q

State three benefits of compression

A

Less storage space require
Less bandwidth required
Shorter transmission time

54
Q

Define lossy compression

A

A method of data compression where data is lost in order to reduce file size, resulting in a loss of quality but smaller file sizes

55
Q

Define lossless compression

A

A method of data compression where data is encoded to reduce file size without losing any information, allowing the original data to be perfectly reconstructed

56
Q

What types of files are suitable for lossy compression

A

Reducing quality is acceptable, such as images, videos, and sound files.

57
Q

How does lossy compression work on photographs?

A

It tries to group similar colours together, reducing the number of colours in the image without significantly compromising the overall visual quality

58
Q

How does lossless compression work on documents?

A

It uses algorithms to analyse the contents, looking for patterns and repetition, such as replacing repeating characters with a single character and the number of occurrences

59
Q

What is an advantage of lossless compression over lossy compression?

A

The file can be returned to its original state without any loss of data quality

Computer Science IGCSE (2 decks)

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