E Error Correcting Codes

The problem of adding reliability to data has already been mentioned in Section 2.12. This appendix discusses general methods for detecting and correcting errors. Reliability is, in a sense, the opposite of data compression, since it is achieved by increasing data redundancy. Nevertheless, many practical situations call for reliable data, so a good data compression program should be able to use codes for increased reliability, if necessary. Every time information is transmitted, on any channel, it may get corrupted by noise. In fact, even when information is stored in a storage device, it may become bad, because no hardware is absolutely reliable. This also applies to noncomputer information. Speech sent on the air gets garbled by noise, wind, high temperature, etc. Speech, in fact, is a good starting point for understanding the principles of error-detecting and-correcting codes. Imagine a noisy cocktail party where everybody talks simultaneously, on top of blaring music. We know that even in such a situation it is possible to carry on a conversation, except that more attention than usual is needed