Unit 1 Data Representation

Question 1

Binary systems

Answer 1

Computer uses binary. Has transistors which have 1s and 0s which are located in the integrated circuits.

Question 2

Hexadecimal uses

Answer 2

• Memory dumps
• Represent colour in HTML
• MAC Addresses
• URL
• Assembly language
• IPv6 Addresses
• Locations in memory

Question 3

MAC Address structure composed of

Answer 3

NN-NN-NN-DD-DD-DD

First part is the organisationally unique identifier (OUI) or the manufacturer ID

Next is universally administered address (UAA) serial number

Question 4

Describe MIDI File

Answer 4

• Musical Instrument Digital Interface
• Stores a set of notes
• Does not store actual sounds
• Data in file recorded using digital instruments
• Sends file to audio synthesiser to play note
• Specifies when each note plays and stops, duration, tempo, instrument type
• Individual notes can be edited

Question 5

Describe JPEG

Answer 5

• Joint photographic experts group
• Standard format for storing lossy compression image
• Maintain decent img quality
• File size = pixels * primary Color’s

Question 6

Describe MP3

Answer 6

• Format for digital audio
• Actual recording of the sound
• Is a lossy compression format
• Recorded using microphone

Question 7

Describe MP4

Answer 7

• It can store multimedia
• Music, videos, text, photos
• Format of lossy compression

Question 8

Describe Parity Check and its limitations

Answer 8

• Method of data transmission
• System could use odd or even parity
• Odd/Even parity is decided and parity bit is added at the end
• When receiver gets data a check is performed
• Bits are counted
• If incorrect data sent repeatedly till server times out

Limitations:

• Transposition error
• When bits still add up to odd/even number
• Even number of incorrect bits

Question 9

Describe ARQ

Answer 9

• Transmitter sends data in packets
• When received it is checked for errors
• If no errors, sends an acknowledgment
• If no acknowledgment received, it sends it repeatedly
• Till server times out

Question 10

Describe check digit

Answer 10

• Data is input with check digit
• Calculation performed on inputted data
• Calculated digit is then compared to a stores value
• If it matches, data entered is correct
• If no match, data entered is incorrect

Question 11

Describe check sum

Answer 11

• Transmitter sums up total group of data before transmission
• Data is sent along with the sum
• Receiver works out sum and compares to stored value from transmitter
• Data should match meaning it’s correct
• If no match data entered is incorrect

Question 12

Memory ascending order

Answer 12

Small - Large

Bit
Nibble = 4 bits
Byte = 8 bits
Kilobyte = 1000 bytes
Megabyte = 1000 kilobytes
Gigabyte = 1000 megabytes
Terabyte - 1000 gigabytes

Question 13

Describe Lossy compression

Answer 13

• A compression algorithm used
• Data will be lost permanently
• Reduce colour depth
• Reduce number of pixels
• Reduce sample rate
• Use perceptual music shaping (removes inaudible sounds)

Question 14

Describe Lossless compression

Answer 14

• Compression algorithm
• No data will be removed permanently
• For example an RLE algorithm may be used
• Repeated patterns are identified and indexed
• Sometimes replaced

Question 15

Describe Bitmap img

Answer 15

• Stores position and colour of every pixel
• Very detailed images used for photos
• Makes them large files
• If compression resolution decreased
• Uses .bmp file

Question 15

Describe Vector img

Answer 15

• Mathematically constructed image
• Uses math formulas to draw shapes and lines
• Results in small file size
• Uses .svg file
• Good for cartoons unaffected by pixelation

Question 16

Why is Lossy better than Lossless

Answer 16

− Lossy decreases the file size more 
− Take up less storage space on webserver/users' computer 
− Quicker to upload/download 
− May not need to be high quality 
− Website will load faster for users 
− Less lag/buffering when watching 
− Takes up less bandwidth to download/upload 
− Uses less data allowance

Question 17

Why is Lossless better than Lossy

Answer 17

− Image if compressed does not become pixelated
− User has the option retain all original data
− Can restore the compressed image into original
− Also reduces file size to an extent