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GCSE - Computer Science > Unit 2 - Data Representation✔️ > Flashcards

Unit 2 - Data Representation✔️ Flashcards

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1
Q

How many bits in a byte?

A

8 bits

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2
Q

How many bytes in a kilobyte?

A

1000 bytes

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3
Q

How many megabytes in a gigabyte?

A

1000 megabytes

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4
Q

What is a hexadecimal?

A

• Hexadecimal (or hex) is a number system which uses base 16

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5
Q

Advantages of using hex rather than binary?

A

• It is much simpler to remember a hex value than a binary value
• It is quicker to write or type since a hex digit only takes up one digit rather than 4 bits
• People are less likely to make an error with fewer digits
• It is easy to convert between hex and binary

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6
Q

What is an overflow and how it is caused?

A

• When the result of an addition is too large for the number of bits the computer works with there will be an overflow error

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7
Q

What hapens with a binary shift?

A

• A binary shift moves all the bits one place to the left or right

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8
Q

What is a character set?

A

• All of the characters that a computer can use are called a character set .

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9
Q

What are the two major character sets?

A

• ASCII
• Unicode

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10
Q

What is ASCII?

A

• ASCII (American Standard Code for Information Interchange) has become the standard code, used worldwide

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11
Q

How many bits are used in extended ASCLL to represent a character?

A

8 bits

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12
Q

How many characters does ASCLL allow for?

A

256

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13
Q

How many combinations with 16 bit unicode?

A

65,536 possible combinations

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14
Q

How many combinations with 32 bit verion?

A

4,294,296 possible combinations

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15
Q

Example of Bitmap file formats?

A

-JPG
-GIF
-PNG

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16
Q

Define a pixel?

A

Pixel is the smallest identificable area of an image - each pixel is a single colour and is given a binary value which repersents that colour

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17
Q

What is each pixel given in an image?

A

A single colour repersented by a binary value

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18
Q

What is resolution?

A

Is the concentration of pixels within a specific area

*Area defined by the image width and height in pixels eg 1920 x 1080

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19
Q

How many colours combinations with 1 bit?

A

1 bit = 2 colours
2 bit = 4 colours
3 bit = 8 colours
4 bit = 16 colours

20
Q

What will a higher bit depth result in?

A

• A higher bit depth gives a greater range of colour and a better quality of image

21
Q

What is megadata and what does it contain?

A

• It is information other than image data that is stored with a file
•includes
-colour depth
-resolution
-date created
-author

22
Q

What is a result of greater resolution?

A

Greater file size

23
Q

What is used to convert inputs to digital signals?

A

Analogue to digital convertor (ADC)

24
Q

What is used to convert signals to outputs?

A

Digital audio convertor (DAC)

25
Q

Why are sounds converted to digital form?

A

• Sounds must be converted into a digital form in order to be stored and processed by a computer

26
Q

What is the sample rate?

A

• The sample rate is the number of samples taken per second
• It is measured in hertz (Hz)

27
Q

What is a sound sample?

A

• A sound sample is a measurement of amplitude of a sound wave at a given time and

28
Q

How is sound sample?

A

• Sound is sampled using a bit depth and sample rate
• The bit depth determines how closely the wave is sampled on the y-axis

29
Q

What is a sounds resolution?

A

• The number of bits (audio bit depth) used to record each measurement is known as the resolution
• More bits used per sample enables the height of the wave to be more accurately measured but increases file

30
Q

How many samples per a second is 1 Hz ?

A

1 Hz = 1 sample per second

31
Q

Effect of frequency on sampling rate?

A

• The frequency or sample rate per second affects the level of detail in the digital representation
• The greater the frequency, the greater the accuracy, and file size

32
Q

Equation for files size?

A

File size (bits) = sample rate x bit depth x duration

33
Q

What is lossy compression?

A

• Lossy compression removes sounds that we can’t easily hear and will not affect quality

34
Q

Issue of lossy compression on sounds?

A

• Lossy compression leaves out some data from the original so can negatively affect the sound quality

-requires a larger uncompressed WAV file

35
Q

Benefit of lossy compression on sounds?

A

• This is useful for storing, downloading or streaming

36
Q

What is lossless compression?

A

• Lossless compression formats are able to reduce the file size when compressed but do not lose any information

37
Q

Three examples of lossless music file formats?

A

•FLAC
•ALAC
•WMA lossless

38
Q

Define a sounds bit depth?

A

• The number of bits available to store each sample is known as bit depth

39
Q

What is compression?

A

• Compression is the name given to algorithms which reduce file sizes
• used heavly with sound,image and video files

40
Q

What is decompression?

A

• Decompression is the process where compressed data is restored to its original format

41
Q

Give the two examples of compression?

A

• Lossy compression (JPG, GIF, MP3)
• Lossless compression (PNG, TIFF)

42
Q

Main issues with lossy compression?

A

• Lossy compression permanently loses some data
• Lossy compression results in small mistakes known as ‘digital artefacts’

43
Q

Main benefit with lossless compression?

A

• Lossless image compression will not lose any of the original data

44
Q

How does lossless compression work?

A

1)finds patterns in the original text
2)encodes each pattern in a dictionary

45
Q

Why are files and data sent via the internet normally compressed?

A

• Download times are reduced
• Data allowances go further
• It is possible to transmit video and music data 
 streams as fast as they are playing

46
Q

Benefits of compression?

A

• fewer packets because there are fewer packets
• Quicker to complete transmission
• Reduces traffic over the Internet
• Images inside web pages appear faster
• Reduces space on disk / servers

47
Q

What causes buffering?

A

• Video or music streaming causes buffering if the download speed is slower than the playback speed

GCSE - Computer Science (10 decks)

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