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CS > T1: Data representation > Flashcards

T1: Data representation Flashcards

1
Q

What is the denary system?

A

Number system based on the number 10

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2
Q

What is the binary system?

A

Number system based on the number 2

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3
Q

What is the hexadecimal system?

A

Number system based on the number 16

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4
Q

uses of hexadecimal and advantage

A

Used for memory dumps, HTML, MAC addresses, web addresses and assembly code/machine code, easier to read/interpret than binary

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5
Q

largest 8-bit and 16-bit binary value

A

255, 65535

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6
Q

How do you convert from binary to denary?

A

Add the powers above the binary number, add up the binary numbers where the 1s appear

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7
Q

How do you convert from denary to binary?

A

Under powers, add 1s from left to right if it can add to the number

or remainder read from bottom up

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8
Q

How do you convert from memory sizes?

binary

A

multiply / divide by 1024

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9
Q

How do you convert from binary to hexadecimal?

A

convert each group of 4 binary digits to a hex value

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10
Q

How do you convert hexadecimal numbers to binary?

A

convert each letter/number into 4-bit binary

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11
Q

How do you convert hexadecimal numbers to denary?

A

Remember the place values and then multiply the hex number by this

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12
Q

How do you convert denary numbers into hexadecimal numbers?

A

divideby 16 and write down remainder, read from bottom up

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13
Q

How is hexadecimal used for memory dumps?

A
  • memory contents are printed out either on screen or using a printer
  • runs diagnostics when a computer malfunction (hex used as it is easier to use than a long string of binary values)
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14
Q

What is HTML used for?

A

hypertext markup language used for when writing and developing web pages (uses tags)

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15
Q

What is MAC addresses used for?

A

to uniquely identify a device on the internet (can be UAA or LAA)
first 6 digits for manufacturer code

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16
Q

How is hexadecimal used for web addresses?

A

ASCII codes can replace the URL (which are hex values)

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17
Q

How is hexadecimal used for assembly code / machine code?

A

makes it easier, faster and less error-prone than writing the code in binary

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18
Q

significance of binary

A
  • any data needs to be converted to binary to be processed by a computer
  • data is processed using logic gates and stored in registers
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19
Q

logic left shift equivalent

A

multiplying denary equivalent binary number by 2 ( x 2^(# of shifts))

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20
Q

logic right shift equivalent

A

dividing binary number by 2 ( / 2^(# of shifts))

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21
Q

how do logical shifts work

A

every bit is shifted over one where the empty one is replaced by a 0, if a 1 is replaced, there is an error as the max amount of shifts have been done

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22
Q

what is lost during a logical shift

A

either the most significant or the least significant bit

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23
Q

what’s the range of two’s complement

A

between -128 (10000000) and 127 (01111111)

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24
Q

convert denary to two’s complement

A
  • if positive, put 0 in the first one and put the other ones in the right areas
  • if negative, put 1 in the first one and put the other ones in the areas to subtract from the -128
  • OR
  • find the positive of that value first and reverse all the 1s and 0s and add 1 at the end
25
Q

convert two’s complement to denery

A
  • for positive and negative, sum up the values where there is a 1
26
Q

addition of binary numbers

A
  • 0+0 = 0
  • 0+1 = 1
  • 1+1= 0 carry 1
  • 1+1+1 = 1 carry 1
  • if in the end, the sum is larger than the preset number of bits allowed, there is an overflow error
27
Q

How many GiB in a TiB?

A

1024 GiB OR 2^10 GiB

28
Q

How many MiB in a GiB?

A

1024 MiB 2^10 MiB

29
Q

What are the uses of hexadecimal?

A

Colour values in photo editing software
MAC addresses
IPv6 addresses
Unicode

30
Q

What is an overflow error?

A

A computer or a device has a predefined limit that it can represent or store (e.g. 8 bits or 255).
Once a values falls outside this limit, an overflow error occurs

31
Q
A
32
Q

What is a character set?

A

Consists of all the letters, numbers and special characters that can be recognised by a computer system.

33
Q

How many characters/bits does the ASCII character set use?

A

128 characters / 7 bits

34
Q

How many characters/bits does the Extended ASCII character set use?

A

256 characters / 8 bits

35
Q

How many characters/bits does the Unicode character set use?

why + drawback?

A

65,356 characters / 16 bits

can represent all languages, requires more bits per character than ASCII

first 128 characters overlaps with ASCII

36
Q

What is sample rate measured in?

A

Frequency in Hertz

37
Q

What is the sample rate?

A

How often the height is recorded (x-axis) / number of samples per second

38
Q

What is the sample resolution?

A

The accuracy to which the height is recorded (y-axis) / number of bits per sample

39
Q

What is sample resolution “measured” in?

A

Bit depth

40
Q

How to calculate file size of a sound file in bytes?

A

(Sample rate x bit depth x Length x # of channels) / 8

41
Q

What is the colour depth of an image?

A

The number of bits required to represent the different colours in the image

42
Q

What is the image resolution of an image?

A

The number of pixels in the image (i.e. the area of the image ~ b x h)

43
Q

How to calculate the file size of an image file in bytes?

A

(Image resolution x Colour depth) /8

44
Q

What file formats use Lossy compression?

A

JPG, MP3, MPG

45
Q

purpose of data compression

A

reduce the file size so that it requires less bandwidth, storage space and shorter transmission time

46
Q

What are the disadvantages of Lossy compression?

A

Detail is permanently lost by permanently reducing the colour depth, resolution or rate

47
Q

When would Lossy compression be used?

A

Music streaming
Online images and video
Image libraries on devices or in the cloud

48
Q

What file formats use Lossless compression?

A

TIF, PDF, GIF, PNG, ZIP

49
Q

What are the advantages of Lossless compression?

A

Original quality is preserved / no information or data is lost

50
Q

What are the disadvantages of Lossless compression?

A

Less significant reduction in file size

51
Q

When would Lossless compression be used?

A

Text documents
Electronic books
High resolution documents

52
Q

How does lossless compression reduce the file size without losing data

A

Run Length Encoding (RLE):
- a form of lossless/reversible file
- reduces size of a string of adjacent, identical data (e.g. repeated colours
in an image):
– first value shows the number of identical data items adjacent to each other
– the second value represents the code of the data item (e.g. in ASCII code)
- RLE is only effective where there is a long run of repeated units/bits.

53
Q

What things does lossy compression get rid of

A
  • sounds outside human hearing range
  • sounds that play at the same time
  • similar shades of colour
54
Q

ibby-bytes in bytes and denary

A
55
Q

normal measures of data storage

A

1 byte is 8 bits. A 4-bit number is called a nibble – half a byte

56
Q

how are sound and images processed

A
  • sound wave sampled and converted to binary to be processed by a computer
  • a series of pixels in an image is converted to binary to be processed by a computer
57
Q

Why is it necessary to reduce file size through compression?

A
  • saves storage space on HDD/SSD
  • faster download/upload
  • reduced file size allows for sending per email
58
Q

Define lossy compression

A

lossycompression is when unnecessary parts of the file are removed, it cannot be reconstructed

59
Q

Define lossless compression

A

lossless conpression is when the file can be reconstructed (e.g. through RLE)

CS (9 decks)

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