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# Hamming code and why it is still used today.

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## Scott Banks

on 25 November 2012

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#### Transcript of Hamming code and why it is still used today.

By Scott Banks Hamming code and why it is
still used today What is Hamming code? How does it work? The rule for Hamming code Why is it still used today? Where is Hamming code used in
computing today? Hamming Code diagram And that's all you need to know
All bit positions that are powers of 2 are used as parity bits: positions 1,2,4,8,16 etc...
All other bit positions are for the data to be encoded:
positions 3,5,6,7,9,10,11,12,13,14,15 etc...
Each parity bit calculates the parity for some of
the bits in the code word. The position of the parity
bit determines the sequence of bits that it alternately
checks and skips. Even parity is used.
General rule for position n: skips n-1 bits, check n bits skip n bits, check n bits, etc...
Position 1 (n=1): skips 0 bits (0 = n-1), check 1 bit (n), skip 1 bit (n), check 1 bit (n), etc...
Position 2 (n=2): skips 1 bit (1 = n-1), check 2 bits (n), skip 2 bits (n), check 2 bits (n), etc...
Position 4 (n=4: skips 3 bits (3 = n-1), check 4 bits (n), skip 4 bits (n), check 2 bits (n), etc...
Position 8 (n=8): skips 1 bit (7 = n-1), check 8 bits (n), skip 8 bits (n), check 8 bits (n), etc...
Because of the simplicity of Hamming codes, they are widely used in RAM.
Hamming code is used to error check and correct ASCII code for characters.
Wireless communication also uses Hamming code

A number of simple error-detecting codes were
used before Hamming codes, but none were as effective as Hamming codes in the same overhead of space. In the diagram above the parity bits are indicated and shows how Hamming code would be used to check an ASCII character Hamming code is a set of error-correction codes that can be used to detect and correct bit errors that can occur when computer data is moved or stored, this is very useful due to the fact that it is able to correct errors. Also using more than one parity bit, an error-correction code can not only identify a single bit error in the data unit, but also its location in the data unit. A more efficient method of error checking and correcting has not been found, and due to the amount Hamming code is used today it is unlikely we will need to change to a new error checking method anytime soon. It provides a good balance between error correction and error detection. Richard Hamming invented a system which can
self correct single errors using a few parity bits
in a bits pattern.
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