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=== Data transmission and storage ===
Locally decodable codes are especially useful for data transmission over noisy channels. The [[Hadamard code]] (a special case of Reed Muller codes) was used in 1971 by [[Mariner 9]] to transmit pictures of Mars back to Earth. It was chosen over a 5-repeat code (where each bit is repeated 5 times) because, for roughly the same number of bits transmitted per pixel, it had a higher capacity for error correction. (The Hadamard code falls under the general umbrella of [[forward error correction]], and just happens to be locally decodable; the actual algorithm used to decode the transmission from Mars was a generic error-correction scheme.)<ref>{{cite web |title=Combinatorics in Space The Mariner 9 Telemetry System |url=http://www-math.ucdenver.edu/~wcherowi/courses/m7409/mariner9talk.pdf}}</ref>
LDCs are also useful for data storage, where the medium may become partially corrupted over time, or the reading device is subject to errors. In both cases, an LDC will allow for the recovery of information despite errors, provided that there are relatively few. In addition, LDCs do not require that the entire original message be decoded; a user can decode a specific portion of the original message without needing to decode the entire thing.<ref name=PIR>{{cite web|url=http://research.microsoft.com/pubs/141305/cacm_2010.pdf |title=Private Information retrieval |author=Sergey Yekhanin}}</ref>
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