Section 3 - Data representation

Question 1

What ascii code can be used to identify the character ‘A’?

Answer 1

65

Question 2

What ascii code can be used to identify the character ‘a’?

Answer 2

97

Question 3

What ascii code can be used to identify the character ‘0’?

Answer 3

48

Question 4

How many bits are used during traditional ascii?

Answer 4

7

Question 5

How many values can traditional ascii store?

Answer 5

128 values. 0-127

Question 6

When using ascii, what can the 8th bit be used for?

Answer 6

error checking

Question 7

When is unicode used opposed to ascii?

Answer 7

When ascii does not have enough characters.
It’s main use would be if you lived in a country that used more than one character set and or did not use english characters

Question 8

Explain the use of parity bits.

Answer 8

Used with ascii coding, an extra parity bit is added as the 8th bit for error detection.
Odd and or even parity can be used

Question 9

Explain odd parity

Answer 9

The parity bit is set so that the total number of 1 bits in the pattern is an odd number

Question 10

Explain even parity

Answer 10

The parity bit is set so that the total number of 1 bits in the pattern is an even number

Question 11

How does majority voting work?

Answer 11

Each bit is sent 3 times
This is used so that if an error is detected it can try to be corrected.
Every triplet of digits is checked and if the majority of bits are 1 then the bit is stored as 1 and vice versa for 0

Question 12

Explain the advantages of majority voting over the use of parity bits?

Answer 12

Error correction in addition to error detection

Question 13

Disadvantage of majority voting.

Answer 13

Triple the volume of data is sent.
If the wrong bit is sent twice in the same triplet then the code will be read wrong and the system will be unable to identify the cause of error without the data being sent all over again