Data Storage Flashcards
1
Q
What are the units in Computer Science
A
Bit
Nibble
Byte
Kilobyte
Megabyte
Gigabyte
Terabyte
Petabyte
Hertz
2
Q
How many bits in a byte
A
8
3
Q
How many bits or bytes in a nibble
A
Half a byte
4 bits
4
Q
How many bytes in a kilobyte
A
1000
5
Q
How many kilobytes in a megabyte
A
1000 kilobytes
or 1 million bytes
6
Q
How many megabytes in a gigabyte
A
1000 megabytes
7
Q
How many gigabytes in a terabyte
A
1000 gigabytes
8
Q
How many terabytes in a petabyte
A
1000 terabytes
9
Q
What are the two only states that a computer can understand
A
Power on
Power off
10
Q
What is the power term called
A
Switches
11
Q
What are switches represented by
A
Power on represents a 1
Power off represents a 0
12
Q
What is the table layout for binary and denary
A
128, 64, 32, 16, 8, 4, 2 1
13
Q
What is denary
A
A whole number
14
Q
What is binary
A
An 8 bit number
15
Q
What is 32 in binary. Show steps
A
128, 64, 32, 16, 8, 4, 2 1
0 0 1 0 0 0 0 0
00100000
16
Q
What is 78 in binary
A
128 64 32 16 8 4 2 1
0 1 0 0 1 1 1 0
01001110
17
Q
How do we convert binary to denary
A
128, 64, 32, 16, 8, 4, 2 1
If there is a 0 under a number, we don’t add that number up. If there is a 1 under the number, we add that number. For example If we have the binary number of
10001001
Substitute this in the table.
There is a 1 underneath 128, 8 and 1, so add all those numbers up, which makes 137. For this example we say that 10001001 is 137 in denary
18
Q
Convert 00100111 into binary
A
39
19
Q
Whats the highest possible denary number and binary number
A
11111111
255
20
Q
What is hexadecimal
A
A number that uses a base of 16. It starts from 0 to 9, then from A to F
21
Q
How do we convert hexadecimal to denary
A
Multiply the left hand digit by 16, then add the units
22
Q
How do we convert hex 7 to denary
A
Multiply 7 and 16.
Then add 10
Hex 7 is 122 in denary form and 7 in decimal form
23
Q
What is hex 27 in denary
A
(2x16) + 7 = 39 in denary form
24
Q
How do we convert denary to hexadecimal
A
Divide the denary number by 16. The remainder gives the units.
25
What is denary 72 in hexadecimal
72/16 = 4.5: 4 remainder 5
45 in hexadecimal
26
How do we convert binary to hexadecimal
1. Take a binary word of 8 bits
11100101
2. Divide into two nibbles of 4 bits
1110 and 0101
3. Convert each nibble into its hexadecimal value
1110 = 14 = E in Hex
0101 = 5 in Hex
11100101 = E5 in Hex
27
How do we convert hexadecimal to binary. What is 3B in binary
Split the two hex characters
3 = 0011 and B = 1011
3B = 00111011
28
What is A5 in binary
A = 10 = 1010
5 = 0101
A5 in hex = 10100101
29
What is hex 21 in binary
2 = 0010 and 1 = 0001
21 in hex = 00100001
30
Why do we use hex
1. It is easier to convert between hex and binary
2. People are likely to make less digit errors
3. Quicker to write and type since hex digit only takes up 1 digit rather than 4 bits
4. Much simpler to remember a hex value than a binary value
5. An advantage for programmers and Computer Scientists
31
How does numbers work on computers
Computers work with a fixed number of bits at a time.
32
What is an overflow error
When the result of the addition is too large for the number of bits that a computer works with
33
What are the two logical binary shift operations
Left shift
Right shift
34
What is a binary shift left
A binary shift left of one bit moves all the bits one place to the left. The vacant bit spaces are replaced with 0
35
How does a binary shift left have an affect on the number
The number is doubled
Eg: 1000 = 8
Shift left once = 10000 = 16
36
What is a binary shift right and what is the effect
A binary shift right of two places halves the number and rounds down each time
Eg:
1000 = 8
Shift right once = 100 = 4
Shift right twice = 10 = 2
Eg: 2
1001 = 9
Shift right once = 100 = 4
Shift right twice = 10 = 2
37
What are the effects of shifts
They can quickly multiply or divide the binary number by 2
38
How are characters represented in binary
Every character on the keyboard is represented by a binary number.
Uppercase letters (capitals) have different values from lowercase letters
Punctuation symbols have their own character code
39
What are the four mandatory components that a computer needs to contain
26 lowercase letters
26 uppercase letters
10 numbers
36 other characters
This creates 98 total characters
40
What is a character set
Collection of characters that a computer recognises from a binary representation
41
What are character sets a set of
Letters
Symbols
Digits
42
What are three major character sets used today
ASCII
Extended ASCII
Unicode
43
What is ASCII
A 7 bit character code, that has 128 different characters that can be encoded.
44
What is ASCII Extended
An 8 bit character code, that has 256 different characters that can be encoded.
45
How are ASCII character codes setup
ASCII codes are normally grouped and ran in sequences.
46
What are some types of character codes
7 bit character code
8 bit character code
16 bit character code
47
How many different characters can be encoded via a 16 bit character code
65536
48
What is Unicode
A new code allowing for many more different characters to be used. It has a 16 bit and a 32 bit character code. The 32 bit version gives over 4 billion possible combinations
49
What can we use Unicode for
Emoji storing
Writing text
50
How many bytes in a Unicode
16 bits = 2 bytes
32 bits = 4 bytes
51
What is an image
A visual representation of something, which can consist of a drawing, painting or picture
52
How are digital images stored on a computer
BMP
JPG
GIF
PNG
TIFF
SVG
AI
PS
53
What is a bitmap image
Images made up of picture elements or pixels
54
What is a pixel
The smallest identifiable area of an image
55
How does a pixel plays its part
Each pixel is a single colour and assigned a binary value that represents that colour
56
Can we change the pixel colour?
Yes. But we have to change the value because the binary value is tied to the original colour
57
What is image resolution
The concentration of pixels within a specific area. The area is defined by the image width and height in pixels
58
How do we create an image
1. Each pixel gets a binary value
2. Each value represents a different colour
3. Using 1 bit per 1 pixel allows only 2 values: 0 and 1
1 = Black
0 = White
This would create a black and white image
59
What is image resolution measured in
DPI (Dots per inch)
PPI (Pixels per inch)
60
How do we increase the number of colours in an image
More bits per pixel = More colour combinations
61
How many colours in 1 bit
2
62
How many colours in 2 bits
4
63
How many colours in 3 bits
8
64
How many colours in 4 bits
16
65
How many colours is a pixel able to represent
A Finite amount of colours
66
What is bit depth
Number of bits in each sample
67
What does a higher bit depth give to an image
Greater colour range
Better image quality
68
What happens when we reduce colour
Size reduction
Fewer bits needed per colour
Fewer bits per pixel
69
What is the effect of modifying the colour depth
The number of colours displayed
70
What is a monochrome image
An image represented in binary as a bit pattern
71
How are colour values of individual pixels expressed
Denary RGB values
Hexadecimal form
72
Why isn't binary sued for monochrome images
Less easier to
Read
Write
Remember
Reduce copied errors
Not used by designers
73
What is the pixel proportion for a monochrome image
A proportion of
Red
Blue
Green
From a distance, it makes up a colour
74
What is image metadata
Data about data. It is information other than image data which is stored within a file
75
What does metadata include
Colour
Resolution
Date created
Author
76
What links file size and resolution
The greater the resolution of the image, the greater the file size
77
What is sound
Continuous and regular vibrations which result in noise
78
What are the two types of sound signals
Digital sound signals
Analogue sound signals
79
What's the difference between the signals
Digital sound is discrete
Analogue sound is continuous
80
How is sound digitized
Repeatedly measuring and recording the sound wave
81
How do we store sound on a computer
Convert sound to digital form
82
What are two types of Analogue to Digital convertors
ADC (Analogue to Digital Convertor) converts input to digital signals
DAC (Digital to Audio Convertor) converts digital signals to output
83
What is a sound sample
A measure of amplitude of a sound wave at a given time
84
What are the units of a sound sample
Bit depth
Sample rate
85
What is the bit depth
The factor that determines how closely the wave is sampled at the y axis
86
What is the sample rate
Number of samples taken per second
87
What is the measurement of sample rate
Hertz (Hz)
1Hz = 1 sample per second
88
What is sample resolution
The number of bits (audio bit depth) used to record each measurement
89
What is the effect of increasing the number of bits per sample
Enables the height of the wave to be more accurately measured, but an increased file size
90
What is another word for sample rate per second
Frequency
91
What is the effect of frequency
Has an effect of the level of detail in the digital representation
92
What is the effect of increasing frequency
The greater the frequency, the greater the accuracy and larger the file size
93
What is file size measured in
Bits
94
How many bytes in a bit
1 bit = 0.125 bytes
95
What is the equation for sound file size
Sample rate x Bit depth x duration
96
How do we get improved recorded sound quality
Large frequency of sound sampling
Great accuracy of recorded wave height
97
What is the effect of increasing the sample rate
More data points recorded
98
Approximately, what can we hear sounds from
20 - 20000 Hz
Younger people can hear sounds at higher frequencies
99
What is another word for height
Amplitude
100
How do we convert music into a file
1. The wave amplitude is measured at regular intervals
2. These are then turned into binary
101
What is the effect of a smaller interval
Larger files
Closer sound to original
Better sound quality
102
What is compression
Reduces the file size of an image or object
103
What is decompression
The process of expanding computer data to its normal size so that it can be read by a computer.
104
What is compression used for
Sound
Images
Video files
105
What happens if we use different compression levels
Different compression levels affect quality of compressed images.
Data elimination
Size reduction
106
Why should we use smaller file sizes
It can improve a site's performance and loading times. The smaller the file size, the faster the performance
107
What are the two types of compression
Lossy
Lossless
108
What is lossy compression
Lossy compression reduces the file size, but deletes as much data as possible, permanently. But it is barely noticeable
109
What are the common file standards for lossy compression
JPEG: Photo use
MP4: Video file format
MP3: Music format
110
What are the advantages of lossy compression
1. Doesn't take up as much file space when compressed
2. Greatly reduces file size
3. They take up less bandwidth so can be downloaded and streamed more quickly
4. Lots of software can read lossy files clearly
5. It is barely noticeable when there is a reduction in size quality
111
What are the disadvantages of lossy compression
1. Data is deleted permanently
2. Decompression is not applicable for lossy compression
3. Text or software files will not work as all the data is going to be deleted as files must retain all information of the original
4. Causes degradation which reduces the image quality
5. Digital artefacts can appear in images and videos
6. Noise is seen when there's contrasting colours
Removal of sound so
7. We can't easily hear the least affect of perceived playback quality
112
What is lossless compression
Lossless compression reduces the file size but doesn't delete any of the original data. It stops metadata and such.
113
What does lossless compression allow us to do
It allows you to restore compressed files to its original form.
114
What are common file standards for lossless compression
PNG: Is used for images and photos which can include transparency
ZIP: Document compression
GIF: Simple images, animations may be included
FLAC/ALAC: Lossless music format (Free Apple)
115
What are the advantages of lossless compression
1. Can be decompressed, restored to original
2. No reduction of quality
3. Can be used on text and software files
4. No data is deleted
116
What are the disadvantages of lossless compression
1. Takes up a lot more space than lossy compression
2. Only a small reduction in file size
