Error Detection

Question

If odd parity is used for ASCII error detection the number of 0's per 8 bit symbol is

a) even

b) odd

c) Indeterminant

Answer 1

if Odd parity is used, there should be odd number of 1's in 8 bit symbol.

so, there should be ODD number of 0's too

Answer 2

There is no compulsion on the number of 1's they can very well be ODD or EVEN the value of parity bit will depend upon the number of 1's.

Lets have a look at it with examples:

case 1: Say 11110000 is to be sent. Since ODD parity is being used we will append a 1 at the end of the data "11110000|1|". The number of 0's in this case is even.

 case 2: Say 11111000 is to be sent. Since ODD parity is being used we will append a 0 at the end of the data "11111000|0|". The number of 0's in this case is also even.

Like this you can take numerous cases and the number of 0's will still be even for odd parity.