 # Techniques of Coding Theory

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Bit strings composed of zeros and ones are the most usual way to represent, change and communicate information. This data however s subject to errors due to a variety of factors, such as deterioration of magnetic tape over time, or a scratch on a CD or DVD. Coding theory uses techniques that can help find the errors. However if there are too many errors, the techniques may not always work. One of the first techniques is the error detecting codes, which adds a parity check bit to the end of the bit string. The idea is to add an extra bit to the end of the code to make it either even or odd. For example, if there are an even numbers of 1’s, a 0 is added to the end of the string, and if there are an odd number of 1’s then a 1 is added to the end of the string. When reading the code, if the will use the parity bit to determine if the correct numbers of 1’s are in the string. If an error is made, the number of 1’s will be odd. A downfall of this technique is that only an odd number of errors will be detected by the technique because if an even number of errors are made, the number of 1’s read will still be even and an error will not be found. The next technique is the error correcting code, which take redundancy into account. It can detect errors and then correct them. By using the triple repetition code, which repeats a message three times, we can decipher a string using the simple majority rule which will compare the bits in the original bit strings and use it to decide if an