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Computing > 2 – Data representation > Flashcards

2 – Data representation Flashcards

1
Q

What is a ‘bit’?

A

A single 1 or 0 is a binary digit, or a bit for short.

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2
Q

What is a ‘byte’?

A

A group of eight bits is called a byte.

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3
Q

What is a ‘nibble’?

A

Four bits, or half a byte, is called a nibble.

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4
Q

What is a kilobyte in bytes and bits?

A

1000 bytes or 8000 bits make a kilobyte

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5
Q

What are the units of scale for bytes in order?

A

Kilobyte (kB),
Megabyte (MB),
Gigabyte (GB),
Terabyte (TB),
Petabyte (PB)

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6
Q

What is 7 in binary?

A

111

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7
Q

What is 30 in binary?

A

11110

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8
Q

What is 2 in binary?

A

10

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9
Q

What is 12 in binary?

A

1100

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10
Q

What is 64 in binary?

A

1000000

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11
Q

What is an overflow error?

A

A computer stores things in memory in a finite amount of space. If you cannot represent the number in that amount of space because it is too big, then overflow occurs.

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12
Q

What does shifting a binary number one place to the right do?

A

Shifting right one place divides the number by 2.

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13
Q

What does shifting a binary number one place to the left do?

A

Shifting left one place multiplies the number by 2.

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14
Q

What would 10011100 (156 in denary) shifted two to the right become?

A

10011100 becomes 00100111 which is 39 in denary

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15
Q

How does hexadecimal work?

A

We can represent every group of 4 bits (known as a nibble) with a single digit.
The smallest value you can hold in 4 bits is 0000. The largest value is 1111. This means that we need to represent the denary values 0 to 15 with a single digit. The trouble is, we only have numerical digits 0 to 9, so to get around this problem we use letters A to F to represent the digits 10, 11, 12, 13, 14 and 15.

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16
Q

How would we convert 182 in denary to hex?

A

182 / 16 = 11 remainder 6

11 is B in hex. 6 is just 6

so 182 denary = B6 hex

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17
Q

Why is hexadecimal used and what is an example?

A

Hex is a lot easier for humans to remember and figure out than binary. The most common application of hex in computing is for colour selection.

18
Q

What is ASCII?

A

American Standard Code for Information Interchange or ASCII for short, is a system where a number is assigned to each character.

19
Q

What is a vector graphic?

A

Vector graphics is a form of computer graphics in which visual images are created directly from geometric shapes such as points, lines, curves and polygons.

20
Q

What is the size of an image?

A

The size of an image is expressed directly as the width in pixels by height in pixels.

21
Q

What is the resolution of an image measured in?

A

The resolution of an image is generally measured in Pixels Per Inch or PPI.

22
Q

What happens if the size of a picture is increased?

A

If the size of a picture is increased, then more pixels will need to be stored in order to maintain the same clarity or resolution. This increases the size of the image file. This is a bitmap image.

23
Q

What is a bitmap image?

A

A bitmap is an array of binary data representing the values of pixels in an image or display. A GIF is an example of a graphics image file that has a bitmap. When the GIF is displayed on a computer monitor, the computer reads the bitmap to determine which colours to use to “paint” the screen.

24
Q

What is colour depth?

A

The number of bits used to store each pixel dictates how many colours an image can contain. 8 bits per pixel will give 256 possible colours. The number of bits per pixel is referred to as the colour depth.

25
How do you work out the minimum required colour depth of an image?
To work out the minimum required colour depth from the number of colours in the image, convert the number of colours to a power of 2. 2 = 2^1 colours 1 bit is required per pixel 4 = 2^2 colours 2 bits are required per pixel 8 = 2^3 colours 3 bits are required per pixel ...
26
What happens if you increase the colour depth of an image?
If the colour depth is increased so more bits are used to represent each pixel, then the overall size of the file will increase. The image will look more accurate to the true colour.
27
What is the resolution of an image?
The resolution of an image is the number of pixels (picture elements) or dots that make up an image. The greater the number of pixels, the sharper the image will be, and the larger the file size of the image.
28
What is metadata?
Metadata means ‘data about data’. When a file is saved, information about the file is saved with it. This could include: * Type of file * Time and date of creation * Creator or author of the data * File size
28
What is metadata (give examples)?
Metadata means ‘data about data’. When a file is saved, information about the file is saved with it. This could include: * Type of file * Time and date of creation * Creator or author of the data * File size
29
What will metadata about an image include?
* The dimensions of the image * The image resolution * The colour depth
30
Are sound waves analogue or digital?
Sound waves are analogue, which means continuously changing.
31
How do we store sound on a computer?
Anything stored on a computer has to be stored in a digital format as a series of binary numbers. To store sound on a computer we need to convert the waveform into a numerical representation. The device that takes real-world analogue signals and converts them to a digital representation is called an **Analogue-to-Digital Converter (ADC)**.
32
How is an analogue signal converted in an ADC? (Analogue-to-Digital Converter)
For sound waves, the analogue signal is converted as follows: * Analogue sound is received by a microphone * This is converted into an electrical analogue signal * The signal amplitude (height of the wave) is measured at regular intervals (sampled) * The values are rounded to a level (quantisation) * The values are stored as a series of binary numbers
33
What is sample resolution?
The sample resolution is the number of bits used to store each sample of the sound wave.
34
What is sample rate?
The more often you take a sample, the smoother the playback will sound. The sample rate is the frequency with which you record the amplitude of the sound, i.e. the number of samples per second.
35
What are factor affecting the size of a sound file?
* Sample Size (length of sample) * Sample Resolution * Sample Rate
36
Why is compression used (3 reasons)?
* reduce the amount of storage needed * allow large files to be transmitted as an email attachment * allow a file to be transmitted in less time
37
What is lossy compression?
Lossy compression is a data encoding method where files are compressed by removing some of the detail.
38
What are examples of lossy files extensions?
.jpg .mp3 .wmv
39
What is lossless compression?
This is a data encoding method where files are compressed but no data is lost – an essential factor for text and data files.
40
What are examples of lossless files extensions?
.png .gif .mov

Computing (3 decks)

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