Data Representation Flashcards

1
Q

What is a natural number?

A
  • All positive whole numbers and zero
  • Can be used for counting
  • N = {0,1,2,3,…}
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is an integer?

A
  • Whole numbers
  • Positive and negative including zero
  • Z = {…,-2,-1,0,1,2,…}
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are rational numbers?

A
  • A number that can be expressed as a fraction
  • Can be positive or negative
  • Zero is a rational number
  • The symbol for rational numbers is Q
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are irrational numbers?

A
  • Cannot be written exactly as a fraction
  • They have no symbol
  • Examples include π or √ 2
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are real numbers?

A
  • All possible real world quantities
  • All members of irrational, rational, integers and natural numbers are real numbers
  • Given the symbol R
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are ordinal numbers?

A
  • Integers used to describe the numerical positions of objects in relation to others
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the decimal number base?

A
  • Base 10
  • Used by humans for counting
  • Uses the ten digits 0 through 9 to represent numbers
  • Often called denary
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the binary number base?

A
  • Base 2
  • Uses only two characters for each digit, either a 1 or 0
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the hexadecimal number base?

A
  • Base 16
  • Uses the digits 0 through 9 and A to F
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Why is hexadecimal useful as a shorthand representation for binary?

A
  • Can represent numbers using far fewer digits than binary or decimal
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is a bit?

A
  • The fundamental unit of information
  • Only takes two values, a 1 or 0
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is a byte?

A
  • A collection of 8 bits
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is a nibble?

A
  • A collection of 4 bits, half a byte
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How many values can be represented with n bits?

A
  • 2^n values can be represented
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the binary prefixes for quantities of bytes?

A
  • Kibi (Ki) = 2^10
  • Mebi (Mi) = 2^20
  • Gibi (Gi) = 2^30
  • Tebi (Ti) = 2^40
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the decimal prefixes for quantities of bytes?

A
  • Kilo (K) = 10^3
  • Mega (M) = 10^6
  • Giga (G) = 10^9
  • Tera (T) = 10^12
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is underflow?

A
  • Occurs when very small numbers are to be represented but there are not enough bits available
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is overflow?

A
  • Occurs when a number is too large to be represented with the available bits
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is ASCII?

A
  • Stands for American Standard Code for Information Interchange
  • Uses 7 bits to represent 128 (2^7) different characters
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How did ASCII become outdated?

A
  • With the advent of the Internet, there was a requirement for an information coding system that could represent character sets other than the Latin alphabet, such as Greek or Arabic
  • ASCII did not have enough bits to represent all of these character sets
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is Unicode?

A
  • Allows the representation of a wide variety of alphabets by computers
  • Uses anywhere from 8 to 48 bits per character
  • Represents a much wider range of different characters than ASCII
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is a parity bit?

A
  • Form of error checking
  • A single bit is added to transmission
  • This bit is used to check for errors in the transmitted data
  • The bit’s value is calculated based on the transmitted data itself
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is even parity?

A
  • The parity bit makes the total number of 1s in the transmitted data even
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is odd parity?

A
  • The parity bit makes the total number of 1s in the transmitted data odd
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What happens if an error is detected in using parity?
- The computer asks the sender to retransmit the data
26
What is a disadvantage of using parity bits?
- If an even number of bits are changed during transmission, the error is not detected
27
What is majority voting?
- Each bit is transmitted multiple times - When received, the most commonly occuring value is taken to be correct
28
What is an advantage of using majority voting over parity bits?
- It doesn't just detect the error but also corrects the error - There's no need for retransmission like when using parity bits - Can correct errors when multiple bits change
29
What is a disadvantage of using majority voting?
- The volume of data being transmitted is increased, increasing the time taken to transmit data
30
What is a checksum?
- A value is appended to the transmitted data - This value is determined by the data itself - Once received, the recipient removes the checksum - A check is carried out to ensure that the checksum matches the transmitted data - If the two do not match, the recipient cannot correct the error itself - The recipient asks the sender to retransmit the data
31
What is a check digit?
- Type of checksum - Single digit added to the transmitted data
32
What is an advantage of using a check digit over a checksum?
- The single digit makes it so that the number of different algorithms to calculate the check digit is reduced
33
What is a disadvantage of using a check digit over a checksum?
- The variety of errors that the method can detect is limited
34
What is the difference between analogue and digital data?
- Analogue data is continuous whereas digital data is discrete - Analogue signals can take any values and change as frequently as required - Digital signals must always take one of a specified range of values and can only change values at specified intervals
35
How is a digital signal converted into an analogue signal?
- A digital to analogue converter is used - The device reads a bit pattern representing an analogue signal - It then outputs an alternating, analogue, electrical current
36
How is an analogue signal converted into a digital signal?
- An analogue signal is outputted via (e.g) microphone - Computers use ADCs to convert the analogue signal into a digital bit pattern - The ADC takes a reading of an analogue signal at regular intervals and records the value in a process called sampling
37
What is sampling?
- Samples are taken at a specific frequency - Given in Hertz (Hz) - Determines the number of samples taken per second
38
What is a bitmapped graphic?
- Images are broken into pixels - Each pixel is assigned a binary value - The value assigned to a pixel determined the colour of the pixel
39
What is the resolution of an image?
- Expressed as a number of pixels per inch - Or the number of pixels in an image
40
What is the colour depth of an image?
- The number of bits assigned to a pixel - The number of different colours that can be represented by n pixels in 2^n
41
How is the storage for a bitmap image calculated?
- Number of pixels x bit depth
42
What is metadata?
- Data about data - Included in the storage size - Includes the image width and height, date creation or colour depth
43
What is vector graphics?
- Geometric shapes and objects are used to create images - Properties for each geometric shape or object in the image are stored in a list
44
Evaluate bitmapped graphics vs vector graphics
- Vector can be scaled without losing quality, bitmapped becomes blurry/pixelated when enlarged - Vector well suited for simple images that use shapes but not photos, bitmapped used for storing photos - Vectors use less storage space than bitmapped
45
What is the sampling rate?
- The number of samples per second - Expressed in Hertz
46
What is the sample resolution?
- The number of bits allocated to each sample
47
How is the size of a sound sample calculated?
- Duration of sample in seconds x sampling rate in Hertz x sample resolution
48
What is the Nyquist Theorem?
- The sampling rate must be at least twice the frequency
49
What is MIDI?
- Stands for Musical Instrument Digital Interface - Used with electronic musical instruments which can be connected to computers - Stores sound as a series of event messages - Each event message represents an event in music
50
What are examples of event messages in MIDI?
- The duration of a note - The instrument with which a note is played - How loud a note is
51
What are the advantages of using MIDI?
- Allows for easy manipulation of music without loss of quality - The instruments on which notes sound can be changed - Duration of notes can be changed - Smaller files than sampled audio files
52
What are the disadvantages of using MIDI?
- Can't be used for storing speech - Results in a less realistic sound than sampled recordings
53
What is lossy compression?
- Files are reduced in size - Some info is lost in the process - Quality is reduced - No limit to amount of compression applied
54
What is lossless compression?
- Files are reduced in size - No info is lost - Quality remains the same - Limit to amount of compression applied
55
What is run length encoding?
- RLE is a form of lossless compression - Removes repeated info - Replaces it with one occurance of the info followed by the number of occurences
56
What is a dictionary-based method?
- Form of lossless compression - Dictionary containing repeated data is added to the file - Results in a reduction of size - The dictionary must be present in the file, increasing the size of the compressed file
57
What is encryption?
- The process of scrambling data so that it cannot be understood if intercepted - This keeps it secure during transmission
58
What is plaintext?
- Unencrypted info
59
What is ciphertext?
- Encrypted info
60
What is a cipher?
- Type of encryption method
61
What is a Caesar cipher?
- Encrypts info by replacing characters - One character is always replaced by the same character - Easily crackable
62
What is a Vernam cipher?
- A one-time pad cipher - Each key should only ever be used once and should be random - The key should be at least as long as the plaintext - Mathematically secure
63
How does the Vernam cipher work?
- Aligning characters of plaintext and the key - Converting each character to binary - Applying XOR operation - Converting result back to a character