What do you mean by error detecting codes? Explain Simple Parity Check with example.

Question: What do you mean by error detecting codes? Explain Simple Parity Check
with example. 

Answer 

Error: 

A condition when the receiver’s information does not match with the sender’s information.
During transmission, digital signals suffer from noise that can introduce errors in the binary bits
travelling from sender to receiver. That means a 0 bit may change to 1 or a 1 bit may change
to 0.

Error Detecting Codes (Implemented either at Data link layer or Transport Layer of OSI Model)

Whenever a message is transmitted, it may get scrambled by noise or data may get corrupted.
To avoid this, we use error-detecting codes which are additional data added to a given digital
message to help us detect if any error has occurred during transmission of the message.

Basic approach used for error detection is the use of redundancy bits, where additional bits
are added to facilitate detection of errors.

Some popular techniques for error detection are:

1. Simple Parity check

2. Two-dimensional Parity check

3. Checksum

4. Cyclic redundancy check

Simple Parity check

Blocks of data from the source are subjected to a check bit or parity bit generator form,
where a parity of :

• 1 is added to the block if it contains odd number of 1’s, and
• 0 is added if it contains even number of 1’s

This scheme makes the total number of 1’s even, that is why it is called even parity checking.