Parity Bit

What is Parity Bit?

• A bit with a value of 0 or 1, that is added to the binary string for error detection purposes.
• It is added to the binary string to make the total number of 1's either even or odd.

What is even and odd parity?

• In even parity setting, if the total number of 1's are even 0 is added. If the total 1's are odd then 1 is added.
• In odd parity setting, if the total number of 1's are odd then 0 is added. If the total 1's are even then 1 is added.

Even parity	Odd parity
Initial value: 10001000 Total 1's: 2 Parity bit to be added: 0 Transmitted value in even parity: 100010000	Initial value: 10001000 Total 1's: 2 Parity bit to be added: 1 Transmitted value in odd parity: 100010001
Initial value: 10111010 Total 1's: 5 Parity bit to be added: 1 Transmitted value in even parity: 101110101	Initial value: 10111010 Total 1's: 5 Parity bit to be added: 0 Transmitted value in odd parity: 101110100
Consider the 7 bit ASCII of some characters: D: 1000100 Total 1's: 2 Parity bit to be added: 0 Transmitted value in even parity: 10001000	Consider the 7 bit ASCII of some characters: D: 1000100 Total 1's: 2 Parity bit to be added: 1 Transmitted value in odd parity: 10001001
K: 1001011 Total 1's: 4 Parity bit to be added: 0 Transmitted value in even parity: 10010110	K: 1001011 Total 1's: 4 Parity bit to be added: 1 Transmitted value in odd parity: 10010111

Error Detection:

• If the total number of one's does not match the parity, then the error is detected and the information has to be retransmitted.
• At transmission side the data is set in even parity and if at the receiver side say it is received with odd parity, then the error is detected.

Initial info	Transmitted info (even/odd parity)	Recieved info (even/odd parity)	Error detected (Yes/No)
1001000	10010000 (even)	10010000 (even)	No
1100101	11001011 (odd)	11101011 (even)	Yes
1101100	11011001 (odd)	11001001 (even)	Yes
1110000	11100001 (even)	11100001 (even)	No