ERROR CORRECTION AND DETECTION in computer networks

• PARITY CHECK:For even parity:if an even number of 1 is present then it is ok else add 1  to make an even number of 1 in the transmitting message.At the receiver side, an even number of 1 is checked if true then ok else error in the message is reflected.                     
• CYCLIC REDUNDANCY CHECK: u will be given a generator function and a binary message . Count digit of generator function(let us say, n), add n-1 zero to the message and divide it.Add the remainder  to the binary message .This is your transmitted message .At the receiver side, it is transmitted message is divide with generator function and if remainder == zero then no error else error in  the message.
• INTERNET CHECKSUM METHOD: Add numbers, convert to the binary, make a group of 4 and do module 2 operation . convert this remainder value to decimal and add it original decimal value. This is your transmitted message .At the receiver side , again do the same technique and at last take the 1's complement of the remainder.If it is all zero then no error else error in transmitting the message.