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AS Level Computer Science > Information Representation > Flashcards

Information Representation Flashcards

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1
Q

Denary Definition

A

base-10 number system that uses values 0-9 to represent each digit.

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2
Q

Hexadecimal definition

A

base-16 number system that uses values 0-9 and characters A-F

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3
Q

3 advantages of hexadecimal

A

*Easy to read, write and understand.
*Shorter way of representing binary
*Easier to debug and locate errors in data.

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4
Q

Name 3 ways in which hexadecimal is used

A

*Define locations in memory
*Colour values
*MAC addresses

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5
Q

Binary definition

A

base-2 number system that uses values 0 and 1.

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6
Q

Bit definition

A

a digit expressed using either 0 or 1 in a binary number system.

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7
Q

Byte definition

A

a group of eight bits treated as a single unit.

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8
Q

Nibble definition

A

a group of four bits.

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9
Q

Binary prefix definition

A

A prefix to define the magnitude of a value. E.g., Kibi, mebi, gibi and tebi representing factors 2^10, 2^20, 2^30 and 2^40 respectively.

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10
Q

How much is one kibibyte?

A

1024 bytes

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11
Q

How much is one kilobyte?

A

1000 bytes

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12
Q

Decimal prefix definition

A

A prefix to define the magnitude of a value. E.g., Kilo, mega, giga, and tera representing factors of 10^3, 10^6, 10^9 and 10^12 respectively.

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13
Q

Binary Coded Decimal definition

A

storage of a binary value representing one denary digit in a nibble.

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14
Q

Where is BCD used?

A

Used in:
screen on a calculator
digital time display
Representation of currency values
Bar codes

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15
Q

Packed BCD definition

A

two BCD nibbles stored in one byte

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16
Q

Overflow definition

A

a condition when the result of a calculation is too large to fit into the number of bits defined for storage.

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17
Q

How many codes could original 7-bit ASCII store?

A

128

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18
Q

Who was ASCII standardised by?

A

American National Standards Institute (ANSI)

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19
Q

What are non-printing or control characters

A

introduced in ASCII to help in data transmission or data handling at computer terminals

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20
Q

For which bit do the uppercase letter codes differ from the lowercase in ASCII?

A

The 5th bit

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21
Q

Standardised version of Extended ASCII and what does it include

A

ISO Latin-1. Accented/modified alphabets. up to 256 codes.

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22
Q

What was unicode developed alongside?

A

Universal character Set UCS scheme

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23
Q

What is the most popular version of unicode?

A

UTF-8

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24
Q

Which unicode codes are the same as ASCII?

A

First 128

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25
Q

What is a character code called in unicode and how is it documented

A

Code point
U+ 4-digit hexadecimal number.

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26
Q

What is a vector graphic?

A

a computer image consisting of drawing objects defined in a drawing list

27
Q

What is vector image created by?

A

drawing package or computer-aided design (CAD) package

28
Q

Drawing list definition

A

contains one set of values for each drawing object. (command (containing list of attributes defining a property) required to draw each object)

29
Q

Drawing object definition

A

a component defined by geometric formulae and associated properties.

30
Q

Define property and list 6 of them

A

defines one aspect of the appearance of the drawing object.
- Position
- Radius
- Line style
- Line width
- Line colour
- Fill colour

31
Q

How are dimensions of objects defined in a vector image?

A

relative to an imaginary drawing canvas.
Image is scalable.
This avoids image distortion.

32
Q

What can vectors only be displayed on?

A

graph plotter

33
Q

What does the SVG format use?

A

XML-based text format to describe how the image should look

34
Q

How are bitmaps stored?

A

2-dimensional matrix of pixels

35
Q

What is a pixel and how is it defined?

A

smallest identifiable component of a bitmap image, defined by two properties - position in the bitmap matrix - colour

36
Q

Image resolution definition

A

number of pixels in the bitmap file defined as the product of the width and height values

37
Q

Screen resolution definition

A

product of the width and height values for the number of pixels that the screen can display.

38
Q

Colour depth definition

A

number of bits that are used to create each colour in an image. (represent one pixel) 16-bit, etc. SQUARED

39
Q

Bit depth definition

A

number of bits used to represent each of the red, green and blue colors. Cubed

40
Q

Pixel density definition and how to calculate it

A

number of pixels per square inch.
1. Add together squares of resolution size
2. Find square root.
3. Divide by screen size

41
Q

What is a file header?

A

set of bytes at the beginning of the bitmap file which identifies the file and contains information about the coding used.
- Width and height measured in pixels
- date stamp
- image resolution
- Bit depth
- Data compression

42
Q

How is sound transmitted?

A

by causing oscillations of particles within the medium

43
Q

How is sound converted to digital data

A

measured sound values being put into sound encoder which has a band-limiting feature to remove high frequencies and then to ADC converter

44
Q

What is determined when turning sound to digital data?

A

Amplitude

45
Q

Analogue data definition

A

data obtained by measurement of a physical property which can have any value from a continuous range of values.

46
Q

Digital data definition

A

data that has been stored as a binary value which can have one of a discrete range of values.

47
Q

Sampling definition

A

taking measurements at regular intervals and storing the value

48
Q

Sampling rate definition

A

the number of samples recorded each second.

49
Q

Sampling resolution definition

A

the number of bits used to record each sound sample. E.g., 16-bit

50
Q

Pros and cons of larger sampling resolution

A

Pros
- Larger dynamic range
- Better sound quality
- Less sound distortion
Cons:
- Takes longer to transmit
- Greater processing power
- Larger file size

51
Q

Abilities of sound editing software

A

-Edit start/stop times and duration
-Alter frequency and amplitude of a sample
-Extract and save/delete part of a sample
-Fade in/out
-Mix and/or merge multiple soundtracks

52
Q

Describe how video is digitalised

A

Camera picks up light from the image and turns it into an electronic signal using light-sensitive sensors. DV cameras signals automatically converted into compressed digital format.

53
Q

Lossless compression definition

A

coding technique that allows subsequent decoding to recreate exactly the original file.

54
Q

Lossy compression definition

A

coding technique that causes some information to be lost so that the exact original file cannot be recovered in subsequent decoding.

55
Q

Describe Huffman encoding

A

Lossless: text is analysed to find the most often used characters which are then given shorter codes. Original stream of bytes becomes a bit stream. Stored in a translation table. Can also compress sound file which is more effective as some values for amplitude occur far more often than others.

56
Q

Describe Run-length encoding

A

Lossless file compression technique to reduce text and photo files. Reduces size of string of adjacent, identical data by:
- Repeated string encoded into two values: number of identical data items and code of the data item
- Only effective when there is a long run of repeated units.

57
Q

What is JPEG?

A

Joint Photographic Expert Group: form of lossy file compression based on inability of the eye to spot certain colour changes and hues. Reduces raw bitmap image by factor of 5-15

58
Q

What is MP3/MP4?

A

file compression for music and multimedia files.

59
Q

How to reduce the file size of movie files?

A

reduce sample resolution/rate and frame rate

60
Q

How to reduce the file size of image files?

A

Crop, decrease colour depth, reduce image resolution

61
Q

What is a multimedia container format?

A

A metafile containing both audio and video that describes how the encoded data is stored.

62
Q

What is perceptual music shaping?

A

a process that is used in lossy compression that removes sounds that are not normally heard by the human ear.

63
Q

What is spatial redundancy?

A

when a sequence of consecutive pixels in the same frame have the same value.

64
Q
A

AS Level Computer Science (1 decks)

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