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Computer Science IGCSE > 1. Data Representation > Flashcards

1. Data Representation Flashcards

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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

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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
In 8-bit two's complement, what is the value of the leftmost column?
-128
26
Define character set
A defined list of characters that can be understood by a computer, where each character is given a unique binary code
27
What is ASCII?
A character set that uses 7 bits allowing it represent a maximum of 128 characters
28
What is the definition of extended ASCII?
A character set that uses 8 bits allowing it to represent 256 characters
29
Define UNICODE
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
What does character encoding mean?
The process of assigning a unique binary code to each character in a character set.
31
Define sampling
The process of measuring and capturing values of an analogue signal at regular intervals.
32
What is an analogue signal?
A continuous signal that can only take on any value within a range, such as a sound wave
33
What does Analogue to Digital conversion (A2D) mean?
The process of converting an analogue signal, such as sound, into a digital form that a computer can understand
34
Define sample rate.
The amount of samples taken per second of an analogue signal, measured in Hertz
35
Define sample resolution
The number of bits stored per sample of the sound
36
Define duration
The length of time that something lasts in the context of sound, it refers to the length of the recorded audio
37
Define bitmap
An image made up of squares called pixels, where each pixel is stored as a binary code
38
What is a pixel?
The smallest element of a bitmap image
39
Define resolution
The total amount of pixels that make up a bitmap image, calculated by multiplying the height and width of the image
40
What does colour depth mean?
The number of bits stored per pixel in a bitmap image
41
State the equation in terms of X for the maximum number of colours in an image with colour depth X
2* (2 to the power colour depth)
42
How many bits are in a byte
8
43
How many bits are in a Kibibyte?
1024 bytes (2^10 bytes)
44
What is the difference between a megabyte and mebibyte?
A megabyte is 1000² bytes, while a mebibyte is 1024² bytes
45
How do you convert bytes to bits?
To convert from bytes to bits, multiply by 8
46
What is a Tebibyte?
2⁴⁰ bytes
47
What is the symbol for Mebibyte?
MiB
48
How do you convert from kibibytes to bytes
Multiply by 1024
49
What is the formula for calculating the size of a bitmap image?
image width × image height × colour depth
50
What is the formula for calculating the size of a sound file?
Sample rate × duration × sample resolution
51
How do you convert file size from bytes to kibibytes?
Divide by 1024
52
Define compression
Reducing the size of a file so that it takes up less space by secondary storage
53
State three benefits of compression
Less storage space require Less bandwidth required Shorter transmission time
54
Define lossy compression
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
Define lossless compression
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
What types of files are suitable for lossy compression
Reducing quality is acceptable, such as images, videos, and sound files.
57
How does lossy compression work on photographs?
It tries to group similar colours together, reducing the number of colours in the image without significantly compromising the overall visual quality
58
How does lossless compression work on documents?
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
What is an advantage of lossless compression over lossy compression?
The file can be returned to its original state without any loss of data quality

Computer Science IGCSE (2 decks)

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