Information Coding System

Question 1

ASCII

Answer 1

uses 7 bits to represent 2^7 different characters (A to Z, 0-9 and various symbols)

Question 2

Why Unicode became needed

Answer 2

Represents a wide variety of alphabets (not just english alphabet)
can use between 8 to 48 bits per character
therefore represents a much wider range of different characters

Question 3

Parity Bits( method of error checking(

Answer 3

single bit added to a transmission that can be used to check for errors in the transmitted data
calculated based on the transmitted data itself

Question 4

Types of Parity Bits

Answer 4

Even (makes sure total number of 1s transmitted are even)
Odd (total number of 1s in transmitted data is odd)

Question 5

Disadvantage of Parity Bits

Answer 5

regardless of type of parity used, if an odd/even number of bits change during transmission the error wont be detected

Question 6

Majority voting

Answer 6

each bit of data is transmitted multiple times
when data is received most commonly occurring value is seen as correct

Question 7

Disadvantage of Majority Voting

Answer 7

Volume of data being transmitted is increased with the repetition of bits
significantly increase the time taken to transmit the data

Question 8

Checksums

Answer 8

Adding a value (determined by data itself) to transmitted data
applying any algorithm to the data sent
e.g. 46 = 101110
46 MOD 8 = 6(remainder) = 110
101110 with 110 at end
= 101110110
recipient can remove checksum and apply same algorithm used to ensure they match
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Question 9

Disadvantage of Checksum

Answer 9

if an error is found, the recipient cannot correct the error themselves so need to request that sender re transmits data

Question 10

Check digits