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11B1/Cp > Binary Representation (Ch9) (M1) > Flashcards

Binary Representation (Ch9) (M1) Flashcards

1
Q

What is a character set?

A

A character set is a list of binary codes that can be recognised by computers as being usable characters

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2
Q

What is ASCII?

A

ASCII is a common encoding system for text and is a standard that was used by many computers worldwide

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3
Q

What does ASC() do?

A

ASC() coverts a string character to an ASCII code value

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4
Q

What does CHR() do?

A

CHR() converts an ASCII code to a string character

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5
Q

What is unicode?

A

Unicode is a character set used to represent all known languages

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6
Q

What is the equation to find the size of a text file?

A

Text file size = bits per character x number of characters

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7
Q

What do computers operate and communicate with?

A

Computers operate and communicate using binary

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8
Q

Why are binary codes used to represent text?

A

Binary codes are used to represent text because letters, punctuation, numbers, and symbols cannot be recognised by a computer

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9
Q

What is the difference between ASCII and unicode?

A

ASCII stores characters as 7 bit values, whereas unicode stores characters as 8 bit ASCII

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10
Q

How many bits was ASCII originally represented with, how has this changed?

A

ASCII was originally represented with 7 bits
This is often now represented with 8 bits by adding a 0 at the beginning

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11
Q

What is the value of “A” and “a” in ASCII?

A

A = 65
a = 97

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12
Q

Why did ASCII store characters as 7 bit values, and then changed to store them as 8 bit values?

A

ASCII changed the amount of bits needed to store a character because computing grew in popularity.
This led to ASCII being extended to 8 bits to allow for: foreign languages, mathematical symbols, and special symbols

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13
Q

In English, what is the same about Unicode and 8 bit ASCII?

A

In English, the first 128 codes in unicode are the same as in ASCII

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14
Q

What is the relationship between the number of characters and the number of bytes?

A

The number of characters (including blank spaces) in the file, equals the number of bytes
1 character = 1 byte

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15
Q

What is a pixel?

A

A pixel is the smallest possible dot on a computer screen, and has a colour

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16
Q

What is resolution?

A

Resolution is the number of pixels per square inch on the computer screen

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17
Q

What is colour depth?

A

Colour depth is the number of bits used to encode the colour of each pixel

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18
Q

What is metadata?

A

Metadata is data about data

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19
Q

What is the formula to find the file size of an image?

A

Image file size = colour depth x image height (px) x image

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20
Q

An image sized 640 x 420 has:

640 pixels in width
420 pixels in height

Calculate the total number of pixels

A

Total pixels = width x height
Total pixels = 640 x 420
Total pixels = 268,800

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21
Q

What is a greyscale image?

A

A greyscale image is where the value of a pixel is a single sample, only representing an amount of light

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22
Q

What is the relationship between the number of pixels and the image quality?

A

The more pixels, the higher the image quality
The less pixels, the lower the image quality

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23
Q

What are bitmap images made up of?

A

Bitmap images are made up of pixels

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24
Q

How can you make a greater range of shades and colours in an image?

A

You can make a greater range of shades and colours by increasing the number of bits per pixel (the colour depth)

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25
What are the common colour depths?
Common colour depths: 1-bit, 8-bit, 16-bit, and 24-bit
26
Most devices use a 24-bit colour depth. How many bits are used for each colour?
8 bits are for the levels of red, green and blue in each pixel
27
What is the formula to find the total number of colours in an image?
Total number of colours = 2^n (Where n = number of bits per pixel (bpp), or colour depth)
28
In 8-bit encoding, how many colour variations are there?
In 8-bit encoding, there are 256 colour variations
29
If 8-bit encoding has 256 colour variations, how many colour variations does 24-bit encoding have?
8 bits = 256 colour variations 24 bits = 256 x 256 x 256 = 16,777,216 colour variations
30
What is 24-bit encoding known as? Why?
24-bit encoding is known as true colour This is because this colour depth can produce more colours than the human eye can see (estimated to be 10 million)
31
What is the formula to find the number of pixels in an image?
Number of pixels = image width x image height x colour depth encoding value (Number of pixels = resolution x colour depth encoding value) P = W x H x D
32
An image that has a resolution of 640 x 420 has a 24-bit colour depth. How many pixels does the image have?
Resolution = 640 x 420 = 268,800 Colour depth = 24 Number of pixels = resolution x colour depth encoding value Number of pixels = 268,800 x 24 Number of pixels = 6,451,200 pixels
33
An image that has a resolution of 640 x 420 has a 24-bit colour depth. What is the file size of the image in megabytes?
Resolution = 640 x 420 = 268,800 Colour depth = 24 Number of pixels = resolution x colour depth encoding value Number of pixels = 268,800 x 24 Number of pixels = 6,451,200 pixels File size = 6,451,200 bytes 1MB = 1,000,000 bytes 6,451,200 / 1,000,000 = 6.4512 (6.4) MB
34
What is the equation to find the file size in bytes?
File size (in bytes) = file size (in bits) / 8
35
What is the equation to find the file size in megabytes?
File size (in megabytes) = file size (in bytes) / 1,000,000
36
What does metadata provide?
Metadata provides information about a file
37
Give 3 examples of metadata for a digital image file
Examples of metadata for a digital image file: Make and model number of the camera Apeture setting (light levels) Speed setting Image dimensions File size Location the image was taken at (GPS)
38
Without metadata, what problem would devices face when using images?
Without metadata, devices would not be able to display the image on screen as intended
39
Why can metadata be a privacy or security risk?
Metadata can be a privacy or security risk because it provides lots of information about a file like the location a picture was taken at. This could be use to track people down or give clues about their location.
40
What do sample rate and bit depth affect about a digitally converted sound wave?
Sample rate and bit depth affect the quality of a digitally converted sound wave
41
What is sound caused by?
Sound is caused by vibrations which cause changes in air pressure
42
What is sample rate?
Sample rate is how often (frequency) you record the amplitude of a sound wave. The more often you record a sample, the smoother the playback will sound.
43
What is frequency?
Frequency is the number of samples taken per second
44
What is bit depth?
Bit depth is the number of bits stored per sample
45
What will happen to the sound and file size, if the bit depth is increased?
When the bit depth is increased, the sound is more accurate and the file size will be higher
46
What is the sampling rate of a CD?
A CD has a sampling rate of 44,100 samples per second (44.1 kHz)
47
What is the equation to find the size of a sample?
Size of sample = number of samples per second x number of bits per sample x length of sample (in seconds)
48
What is analogue?
Analogue is data that can use any value in a continuous range
49
What is sampling?
Sampling is making a physical measurement at timed intervals and converting the measurement to digital values
50
What is duration?
Duration is how many seconds of audio the sound file contains
51
What is the equation to find the size of a sound file?
Sound file size = sample rate x duration x bit depth
52
What is the relationship between waves per second and pitch?
The more waves per second, the higher the pitch
53
Give one example of analogue sound
Examples of analogue sound: Vinyl albums, audio cassettes, a human voice
54
How is sound recorded?
Sound is recorded by a microphone as an analogue signal
55
Analogue signals need to be converted into digital data. Why? How is this done?
Analogue signals need to be converted into digital data This is so computers can read and store sound files This is done by analogue to digital converters, which are found in most modern recording devices
56
Give 3 advantages of sampling
Advantages of sampling: Can be edited by a computer Portability - can be stored on a portable device like a memory stick Repeated play time doesn't lead to deterioration Copies can be made on a computer Can be emailed/uploaded/downloaded/streamed Equipment needed is cheap, home microphone and speakers/headphones widely available
57
Give 1 disadvantage of sampling
Disadvantages of sampling: Doesn't contain all the original sound information, some is always lost but this can be minimised through use of a high sample rate and bit depth
58
Justify when it may be better to use higher and lower sample rates
When you have low storage, using a lower sample rate may be more useful. But if you are recording a high quality piece of music, a high sample rate would work better for a higher quality of sound
59
Calculate the size (in KB) of an audio file of a song lasting five minutes which is sampled at a rate of 41,100 samples per second and a bit depth of 24 bits. Show your working out.
Sample rate = 41,100 Duration = 5 minutes = (60 x 5 = 300) 300s Bit depth = 24 bits Size of sample = ? Size of sample = sample rate x duration x bit depth Size of sample = 41,000 x 300 x 24 Size of sample = 295,200,000 bits 295,200,000 / 8 = 36,900,000 bytes 36,900,000 / 1000 = 36,900 kilobytes
60
A stereo song has to be recorded at CD quality. The song is 3 minutes and 42 seconds long. What file size would the song have?
Sample rate = 44.1 kHz = 44,100 Hz Duration = 3 minutes, 42s = (60 x 3 = 180) 180 + 42 = 222s Bit depth = 16 bits File size = Sound file size = sample rate x duration x bit depth Sound file size = 44,100 x 222 x 16 Sound file size = 145,987,200 bits 145,987,200 / 8 = 18,248,400 bytes 18,248,400 / 1000 = 18,248.4 kilobytes
61
What is compression?
Compression is reducing the file size for file storage or upload/download optimisation
62
In terms of data loss, what is the difference between lossy and lossless compression?
Lossy: Data is lost in the compression process and when the file is decompressed it will not contain all of the original information. The original file cannot be restored. Lossless: No data is lost and the file can be decompressed with all its information intact. The original file can be restored.
63
Why is lossy compression not suitable for text or program files?
Lossy compression causes irreversible change where data is lost. This makes it not suitable for text or program files.
64
What are the two techniques for lossless compression?
The two techniques for lossless compression are: Dictionary encoding Run length encoding
65
Give one example of a file type that uses lossless compression
Files that use lossless compression: PNG, Bitmap, GIF
66
Give one example of a file type that uses lossy compression
Files that use lossless compression: JPEG, MP3
67
Give 3 benefits of compression
Advantages: Less bandwidth required when downloading Transfer speed is quicker (e.g. emailing photos, uploading photos) Uses less storage space (e.g. on servers/hdd) Reduce internet congestion Enable streaming of audio/video (e.g. NETFLIX, BBC iPlayer)
68
What is redundancy?
Redundancy is the number of items of data in a file which are the same
69
What is a run?
A run is a sequence of repeated characters
70
How does lossy compression work on image files?
The lossy compression algorithm works on an image by: Analysing the image and finds areas with slight differences (e.g. similar colours) Gives them the same value (e.g. makes them the same colour value) The file is then rewritten using fewer bits
71
Give two features of lossy compression
File size is decreased by permanently removing some of the data The original file can never be restored after decompression Suitable for graphic and audio files
72
How does lossy compression work on sound files?
The lossy compression algorithm works on sound files by: Removing slight differences in volume and frequency These differences are usually undistinguishable
73
What are most digital images stored as?
Most digital images are stored as bitmaps
74
How does lossless compression work on images?
Lossless compression stores the binary for a colour value, followed by the number of pixels of that colour in a row It checks for redundancy
75
What cannot happen to text documents and executable code during compression?
During compression, text or executable files cannot permenantly lose data
76
What do 1s and 0s in a computer represent?
Computers use 1s and 0s to represent the flow of electricity.
77
How many bits are in a nibble?
There are 4 bits in 1 nibble
78
How many bits are in a byte?
There are 8 bits in 1 byte
79
How many bytes are in a kilobyte (KB)?
There are 1000 bytes in 1 kilobyte (KB)
80
How many bytes are in a kilobyte (KB)?
1000 bytes are in 1 kilobyte (KB)
81
How many kilobytes (KB) are in a megabyte (MB) ?
There are 1000 kilobytes (KB) in 1 megabyte (MB)
82
How many megabytes (MB) are in a gigabyte (GB)?
There are 1000 megabytes (MB) in 1 gigabyte (GB)
83
How many gigabytes (GB) are in a terabyte (TB)?
There are 1000 gigabytes (GB) in 1 terabyte (TB)
84
How many terabytes (TB) are in a petabyte (PB)?
There are 1000 terabyes (TB) in 1 petabyte (PB)
85
Calculate how many bits are in a gigabyte
1GB = 1000MB 1000 x 1000 = 1,000,000KB (1GB = 1,000,000KB) 1,000,000 x 1000 = 1,000,000,000 bytes 1GB = 1,000,000,000 bytes
86
Express 2048MB in GB
2048 / 1000 = 2.048GB 2048MB = 2.048GB
87
An image file has a size of 213,624,133 bits. Convert this file size into megabytes.
213,624,133 / 1000 = 21,362.4133 bytes 21,362.4133 / 1000 = 2.13624133 megabytes

11B1/Cp (15 decks)

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