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Flashcards in Data Representation Deck (14):
1

What are the advantages of the design, manufacture and use of a computer system being based around the binary counting system rather than the denary (human- 0-9) counting system?

1. Computer circuitry is easier to design and build due to the easy mathematical rules of binary such as there only being four possible combinations when adding two binary digits.
2. A computer system is not affected by voltage fluctuations as there are only two states and so a small change in voltage would have no effect on the values stored.
3. Easier design and manufacture of storage devices which use only two states

2

How are integers stored?

Using simple binary numbers. They are commonly stored as 8, 16, 32, 64 or 128 bit binary numbers.

3

How are negative integers stored by a computer system?

Several methods - most common is twos complement where the left-most sided bit is used to store the negative equivalent of that column. For example, -128 would be used to make -19 (-128, 64, 32, 8, 4)

4

How are real numbers stored by a computer system?

Using floating point notation, for example 345765000 would be stored as 3.45675x10^8 which would be stored as two separate integers - split into the mantissa and exponent with a set number of bits e.g if 32 bits are used then 24 bits may be allocated to the mantissa while the remaining 8 bits would be the exponent part of the number. This can be stored using twos complement also in order to allow negative values to be stored.

5

How is text stored by a computer system?

Using binary number code to represent each character. Examples include American Standard Code for Information interchange which is an 8 bit code used to store 256 different text characters and Unicode which is a 16 bit code capable of storing 65 536 characters, numbers and symbols.

6

Why does a computers system store and process data in binary form?

A computer system consists of microscopic switches called transistors which are used in computer circuitry to store and process all data. A switch only has two states (on and off) meaning that all data stored and processed by a computer system is represented using binary values that compromise the digits 0 (off) and 1 (on)

7

How are vector graphics stored by a computer system?

Regular shapes (Polygons, Elipses, Text) and stored by saving a list of attributes for the shape
Irregular shapes are created in a vector graphics application by manipulating a series of nodes and curves which are altered by moving handles attached to each curve. The position of these nodes is then saved.

8

How are sound files stored by a computer system?

To store sound as digital data, an analogue sound must be converted into a series of binary values by:
Taking regular 'samples' of single points on the wave and converting the amplitude of the wave at each point into a binary number.
A stereo sound with left and right channels will store samples for two waves

9

How is the sound quality of a digitised sound determined?

Sample Rate - How often a sample is taken
Sample Depth - This determines the number of different values that may be used in order to store the amplitude of the wave
Higher sampling rate and depth indicate a higher quality sound - this means that the steps in the digital wave may be so small that the wave will closely resemble the original analogue wave. A lower quality sound will have larger steps between each sampled point.

10

How are storage requirements for the size of a sound file calculated?

Number of channels x Sample Depth x Sample Rate x Sample Rate x Time (Seconds)

11

How is the storage requirements for a graphic file calculated?

Resolution x Colour Depth

12

How are video files stored by a computer system?

Uncompressed videos are stored as a sequence of still bit-mapped graphics.
Number of graphics stored is determined by the frame rate and video length

13

How are storage requirements for a video file calculated?

Size of video file = Resolution x Colour Depth x Frame Rate x Time

14

What does a bit-mapped graphic consist of?

Rows and columns of coloured pixels
Each pixel stored as a binary number
Number of possible colours being determined by the number of bits used to store each pixel
Known as its colour depth