1.1.3 Data Storage: Error checking

1.1.3 Data Storage: Error checking

1. Parity check

   • Parity checking is used to check weather data has been changed or corrupted following transmission from one device to another
   • A byte of data is allocated a parity bit o Systems that use even parity have an even number of 1-bits o Systems that use odd parity have an even number of 1-bits

2. Automatic Repeat Request (ARQ)

   • ARQ used acknowledgment to indicate data receiver correctly.
   • It uses and acknowledgement (message sent by the receiver indicating that data has been received correctly)

3. Checksum

   • Data is sent in blocks and an additional value sent at the end of the block
   • An additional value called Checksum, is end at the end of the block of data.
   • The checksum is based on the number of bytes in the block
   • If the checksum at the receiver’s end doesn’t match the checksum at the end of the data block, then an error in transmission has occurred

4. Echo check

   • Data is returned to the sender