# What is Checksum and Working of Checksum

A checksum has another name called hash sum which is applied to a small block of digital data to detect errors occurs during the transmission or storage of data. When you download the files from server/source, the working of checksum applies; a sequence of bits to verify data.
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## Working of Checksum Checker:

The below points describe how checksum checker know that the received data unit is undamaged.
1. The sender subdivides data units into equal segments of ‘n’ bits(16 bits).
2. These segments are added together using one’s complement.
3. The total (sum) is then complemented and appended to the end of the original data unit as redundancy its called checksum.
4. The extended data unit is transmitted across the network.
5. The receiver subdivides data unit and adds all segments together and complement the result.
6. If the intended data unit is intact, total value found by adding the data segments and the checksum field should be zero.
7. If the result is not zero, the packet contains an error & the receiver rejects it.

## Procedure of Checksum:

Checksum Procedure to yields, take input data called checksum algorithm or function. Checksum algorithm if it's great written then it will output different value, even for small changes made to input. This is especially true of cryptography hash functions, which may be used to detect many data corruption errors and verify overall data integrity; previously computed checksum matched the current computed checksum, so it's confirmed that data is not probability accidentally altered or corrupted.

### Working Example of Checksum

Q.Find the checksum for the following bit sequence. Assume a 16-bit segment size.
1001101101010101 0001010101110011

Solution:
1001101101010101

0001010101110011

10011011 00010101

01010101 01110011

Sum  11110000

Sum  10001000

Checksum  00001111

Checksum  01110111

100110110101010100001111

000101010111001101110111