parity

Concept

Single-bit parity

• whether there should be an even/odd number of 1s
• detect single bit errors/odd number of bit errors
• cannot detect even number of bit errors

• weakness: errors occur in bursts, 50/50 if can detect or not

2d parity

• rows and columns
• detect and correct single bit errors
• detect two bit errors
• compute parity bit for all rows and columns

can be computed from the row or column parities