Data Storage Technology: Usually, we think of communications science as dealing with the contemporaneous exchange of information among distant parties. Though, many of the same methods utilized in data communications are too applied to data storage to make sure that the retrieval of information from a storage medium is accurate. We find, for illustration, that similar types of error-correcting codes employed to protect digital telephone transmissions from noise are as well employed to guarantee correct readback of digital data from compact audio disks, CD-ROMs, and tape back-up systems.