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Computer science paper 1 > Data representation > Flashcards

Data representation Flashcards

1
Q

Use of the Hexadecimal System

A
  • Colour codes in HTML
  • Media Access Control (MAC) addresses
  • Memory Dumps
  • Display error codes
  • IPv6
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2
Q

Why is Hexadecimal used?

A
  • Easier to understand and write by user
  • It takes up less space on user screen display
  • Easier to debug
  • Less likely to make a mistake
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3
Q

what is ASCII

A

ASCII is a character set which assigns a unique 7-bit binary code to each character

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4
Q

Why data input in computer needs to be binary?

A
  • Computer consists of logic gates
  • That processes only two values 0 (off) and 1 (on) only
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5
Q

text to binary

A
  • computer uses a character set
  • which is a collection of characters and the corresponding binary codes that represent them
    (for the key pressed)
  • can be processed by computer
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6
Q

Limitations of ASCII

A
  • number of characters it can represent is not enough
  • it does not support characters from languages other than English
  • so Unicode was developed
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7
Q

Unicode

A
  • has different languages, emojis, symbols, greater range of characters than ASCII
  • Unicode requires more bits per character than ASCII (Up to 32 bits)
  • Can result in larger file sizes and slower processing times
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8
Q

converting sound (analogue) to binary (digital)

A
  • process called sampling is used:

1) taking measurements of the sound wave at regular intervals

2) converting these measurements into binary data

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9
Q

sample rate def:

A

number of samples taken per second

units: Hz

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9
Q

What does accuracy of the recording and the file size depend on?

A

Sample rate

Sample resolution

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10
Q

what is bitmap image made up of

A

Series of pixels, which are small coloured dots arranged in a grid.

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11
Q

what is each pixel represented by?

A

a binary code, which is processed by the computer

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12
Q

Image resolution def:

A

number of pixels in the image

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13
Q

Higher image resolution does what

A

has more pixels

sharper and more detailed, more realistic

but also requires more storage space and file size

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14
Q

colour depth def:

A

number of bits used to represent each colour

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15
Q

Higher colour depth does what

A

more colours can be represented

resulting in more realistic image

but also requires more storage space and file size

16
Q

what happens to file size of image if colour depth and image resolution increases and why?

A

Increases:

because more pixels and colours require more binary data to represent them

17
Q

what happens to quality when colour depth and image resolution increase?

A

increases

(however quality should be limited by file size for storage space)

18
Q

calculating file size of image file:

A

pixels height x width x colour depth to get total number of bits

Divide the total number of bits by 8 to get the file size in bytes

then multiply by 1024 to convert into KiB or MiB etc..

19
Q

calculating file size of sound:

A

sample rate x sample resolution x duration (seconds)

Divide total number of bits by 8 to get the file size in bytes

then multiply by 1024 to convert into KiB or MiB etc..

20
Q

Why data is compressed?

A
  • reduce large file size
  • less bandwidth required
  • less storage space required
  • shorter transmission time
  • faster processing time
21
Q

Loseless compression def:

A

compression algorithm used to reduce the file size without permanently removing data

22
Q

loseless compression process:

A

using run-length encoding (RLE) algorithm

Repeated patterns in the file are grouped and indexed

The data is replaced with the index and positions stored

23
Q

Run-length encoding
what it does:

A

replaces sequences of repeated characters with a code that represents the character and the number of times it is repeated

24
Q

Lossy compresison:

A

reduces the file size by permanently removing some data from the file

25
Q

when is lossy compression used?

A

images and audio files where minor details or data can be removed without significantly impacting the quality

26
Q

how does lossy compression compress

A

a compression algorithm is used to remove unnessecary data permenanetly, that users wont notice
by:

reducing colour depth or image resolution

or

reducing the sample rate or sample resolution

27
Q

When is lossy or loseless used?

A

Lossy compression = media files (sound and image)
where minor data loss is acceptable if it does not impact quality

Lossless compression = used for text and code
where no data can be lost

28
Q

MP3 file features

A

Contains metadata

Uses lossy compression

Contains actual sound

29
Q

Character set

A

All the characters and symbols that can be represented by a computer system and are assigned a unique value each

30
Q

Why does Unicode require more storage space than ASCII

A

Each character is encoded using more bits

31
Q

Sample resolution def

A

number of bits per sample, that defines the number of different amplitudes that can be recorded

32
Q

Advantage and Disadvantage of higher sample resolution and sample rate

A

ADV:
- The recording of the sound is more accurate and closer to original

DISADV:
- The file size will be increased
- The file will require more storage space

33
Q

Hexadecimal use in website development

A

− To represent HTML colour codes
− In error messages

34
Q

Hexadecimal use in low-level language programming

A
  • Memory address locations
  • In error messages
  • Memory dump
35
Q

Overflow error

A
  • A register has a predetermined number of bits and there are too many bits for it
  • The result of the calculation is greater than 255
36
Q

How a digital image file is stored by a computer

A
  • Image is made of pixels
  • Each pixel stores one colour
  • Image has a set number of pixels wide by pixels high
  • Each colour has a unique binary value
  • The binary value of each pixel is stored in sequence
37
Q

How analogue sound is recorded and converted into a digital file

A
  • recorded using a microphone
  • The sound wave is sampled
  • measures the amplitude of the wave
  • Each amplitude has a unique binary value
  • The sample rate is set
  • that is the number of samples taken per second
  • The sample resolution is set
  • that is the number of bits used per sample
  • Each sample taken is converted to binary

Computer science paper 1 (14 decks)

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