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Computing > A451: Topic 4 - Representation of Data > Flashcards

A451: Topic 4 - Representation of Data Flashcards

1
Q

Why do we use hexadecimal to represent binary?

A
  • it is 4 bits per hex digit / straightforward to convert

• shorter number to remember/quicker to enter/less susceptible to error.

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2
Q

Explain the term character set?

A

All the characters which are recognised/can be represented by the computer system.

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3
Q

What is the ASCII character set?

A

Some computers use the American standard code for information interchange format to use binary codes to represent numbers, letters and special characters. It uses 8-bit to represent each character . The problem is this is there is a low limit to how many characters you can have. 256 symbols. Code is then represented as binary.

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4
Q

What is UNICODE character set?

A

UNICODE is a character set that can handle any language and it does so by the user selecting a specific ‘code page’ which is one portion of the total Unicode space. This way all languages can by displayed so it is universal.

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5
Q

Why is binary used to represent characters?

A

This is because computers can only think in binary. A negative or positive.

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6
Q

Why does all data need to be turned into binary to be processed?

A

This is because computers can only think in positive and negative. 0’s and 1’s.

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7
Q

Explain the need for metadata?

A

For a picture, metadata is needed to be included in the file about height width and color depth. Metadata is included in the image because without it the computer will not no how to display the image.

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8
Q

What is metadata?

A

information about data, in this case information e.g. when it was written and who by.

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9
Q

Why do pictures need metadata?

A

This is so the computer knows how to assemble the picture and also who the picture was taken by etc.

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10
Q

What is Color depth is measured in?

A

Bits per pixels.

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11
Q

How do we use binary to represent images?

A

WE can use binary numbers to represent each pixel. For example in a simply image where there are only two colors (color depth of 1) then we can simply use 1 for for one color and 0 for another.

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12
Q

Image meta data height and width?

A

the height and width of the image in pixels.

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13
Q

Image metadata color depth?

A

The number of bits available to represent each pixel.

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14
Q

Image metadata resolution?

A

The Pixels per inch PPI. if the PPI is high, then the resolution and image quality is also high.

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15
Q

What is JPG used for?

A

Used to transmit image file.

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16
Q

What is BMP used for?

A

Used to transmit image file.

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17
Q

What is MP3 used for?

A

Used to transmit sound file.

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18
Q

What is AVI used for?

A

Used to transmit video file.

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19
Q

What does ASCII stand for?

A

It stands for the American Standard Code for Information Interchange Character set.

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20
Q

The more bits in the color depth…

A

the more colors can be displayed, there for the picture looks more vibrant. More bits are used to represent colors

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21
Q

1-bit color depth can display how many colors?

A

2 colors

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22
Q

8-bit binary set can display…

A

256 colors, (one for each binary number from 00000000 to 11111111)

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23
Q

If the image has a higher resolution…

A

It has more pixels to store data about and is therefore a larger size.

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24
Q

If the image is lower resolution…

A

This means that there are less pixels per inch, which means less pixels to store data about and is therefore smaller in size.

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25
Q

ASCII is a…

A

8 bit binary character set.

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26
Q

Bits per pixel is the…

A

Color depth.

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27
Q

How is sound stored in computers?

A

Sound is stored in the computer by taking taking samples of the sound wave at regular intervals and converting those into binary numbers. Using an analogue to digital converter the computer can then re-creates the sound by reversing the process.

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28
Q

What is the sample rate?

A

The sample rate refers to the number of samples taken per second ,it is measured in hertz. This is like the clock speed on the CPU.

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29
Q

What happens if the soundwave is not sampled at a high enough rate?

A

This can lower the quality of the sound recording but the file size is smaller.

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30
Q

If the soundwave is sampled at a higher sampling rate…

A

This will increase the quality of the recording but the file size would be much larger.

31
Q

What is the bit rate?

A

The bit rates refers to the amount of bits used to store the different levels of sound at the sampling interval. the more bits greater range of levels that can be distinguished. This also has the effect of increasing the file size.

32
Q

Why do programmers use hexadecimal? (3)

A
  • Binary produces long strings, hex is shorter.
  • Binary is difficult to work with
  • Hex can be easily converted to and from binary
  • Hex is less susceptible to error
33
Q

To convert binary to hexadecimal you need to…

A

Break it down into nibbles, blocks of four bits.

34
Q

What is the ASCII character set not good?

A

This is because it is only a 8 bit binary set around 256 variations.

35
Q

Explain the use of Binary codes to represent characters?

A

Every time a character is entered on the keyboard a code is transmitted to the computer. The code numbers are stored in binary. Different sets of code are available for different sets of computers.

36
Q

What is EBCDIC?

A

This is Extended Binary Coded Decimal Interchange Code, an 8-bit encoding system that has 2 to the power of 8 (255) different characters in its character set.

37
Q

What is a ADC?

A

An analogue to digital converter. It takes real world signals and converts them into digital representation.

38
Q

Define Sample Resolution?

A

The number of bits used to store each sample. the more bits used the better the accuracy of the file.

39
Q

Define Sample interval?

A

The time period between taking samples/measurements. The more frequently the sound is sampled, the better the quality of playback.

40
Q

Explain how the computer knows the difference between instructions and data?

A

The operating system is used for memory management. Every location in memory has a unique address. The operating system knows where the data and the programs are located in main memory.

41
Q

Define Binary?

A

Base 2 number system, used by computers, uses 1’s & 0’s only.

42
Q

Define Deanery?

A

Base 10 number system, how we normally count, uses digits 0-9.

43
Q

Define Hexadecimal?

A

Base 16 number system used by humans to represent groups of four bits at a time, uses 0-F.

44
Q

Define Overflow?

A

When the result of a numeric calculation is too large to be stored in the space reserved for that type of data.

45
Q

Define Bitmap image?

A

An image that has been stored as a series of values per pixel. The color of each individual pixel is stored in a file.

46
Q

Define Vector Graphic?

A

An image that is made of lines and shapes that have a certain properties, for example, a line may have the following properties: start-point, end point, line color, line thickness, line style. The properties of each shape are stored inn a file to make up the image.

47
Q

Define Pixel?

A

Short for picture element. It is the smallest component of a bit-mapped image.

48
Q

Define Analogue sound?

A

A continuously changing wave such as natural sound.

49
Q

Define Digital sound?

A

Data that is made up of separate values. How data is stored on a computer.

50
Q

What is data?

A

Facts and figures with no context of format to give them meaning.

51
Q

What is information?

A

Processed data that has context and format so that it conveys meaning.

52
Q

What is an instruction set?

A

The group of instructions available for that specific processor to use. The number of instructions available will depend on the number of bits used. For example, with bits there could potentially be 15 different instructions.

53
Q

What is a Op code?

A

The group of bits in an instruction that represents the operation such as Eat, Move. etc.

54
Q

What is a compiler?

A

A piece of system software that converts a program written in a high level programming language into machine code (binary).

55
Q

What is Machine Code?

A

A binary representation of a program.

56
Q

What is High level Programming language?

A

A programming language written in constructs using language we can understand. Languages include Delphi, Visual Basic, Java and C++.

57
Q

Explain why computers use binary?

A

So that computers can be based on logic circuits.
… ( each part of the circuit) can be in one of two
states
… 0 and 1/true or false

58
Q

Describe how instructions are represented in binary?

A 
The instruction consists of an operator/op code
 ... and an operand
 both stored as bit patterns
 (op code) from a given instruction set
 Each op code has a unique bit pattern
59
Q

What is meant by a real number?

A

A number containing a fractional part.

60
Q

What is meant by an integer?

A

A whole number.

61
Q

Describe two differences between high level code and machine code?

A

In high level code Instructions use words
In machine code instructions are in binary code

High-level code is designed to be read by human
programmers
Machine code is to be read/executed by the
computer .

62
Q

Five advantages of a digital sound recording over an analogue one?

A
  • Potential for very low distortion.
  • Better sound from cheaper equipment.
  • Data can be cloned.
  • Data can be sent over network.
  • Large range of multimedia tools.
63
Q

Bit depth CD audio?

A

16

64
Q

Bit depth DVD and Blu-ray?

A

24

65
Q

What depth?

A

Bit depth is the number of bits available for each sample. The higher the bit depth, the higher the quality of audio.

66
Q

Sample rate for standard audio CD’s?

A

44.4 kilohertz, forty thousand and 400 snapshots per second.

67
Q

Uncompressed file formats?

A

PCM, WAV

68
Q

Explain the difference between the character sets of Unicode and ASCII. (2)

A
  • Unicode has a much larger character set and can represent many more characters/characters from all alphabets.
  • Because unicode uses 16 bits and ASCII uses fewer/7/8 bits.
69
Q

In most images data is stored about the levels of three colours.
State what these colours are.

A

Red, Green, Blue

70
Q

When image files are transferred on the Internet, they are usually compressed.
Explain why this is done?

A

It reduces the size of the file which needs to be transmitted.
It shortens download time.
It reduces Internet traffic (and hence probability of lost packets).

71
Q

Types of compression and examples.

A

Lossy – when uncompressed it is not exactly the same as the original. (1)
JPEG, GIF. (1)
Lossless compression – when the data is uncompressed it is restored completely totheoriginal file (1)
RAW, TIF, BMP, PNG.

72
Q

Two things stored in image metadata?

A

Data

Camera name and model

73
Q

DESCRIBE what is meant by an overflow

A

There is an extra bit.

As a number can’t fit into 8 bits.

74
Q

MPEG:

A

Videos

Computing (15 decks)

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