Red Book is the standard for audio CD (Compact Disc Digital Audio System).
It is named after one of a set of colour-bound books that contain the technical specifications for all CD and CD-ROM formats.
The physical parameters and properties of the CD are specified as well as the form of digital audio encoding (16-bit PCM), the optical 'stylus' parameters, deviations and error rate, modulation system and error correction, and subcode channels and graphics.
The other books in the set are Yellow Book (CD-ROM and CD-ROM XA), Orange Book (CD-R and CD-RW), White Book (Video CD), Blue Book (Enhanced Music CD, CD+G and CD-Plus), Beige Book (Photo CD, Kodak and Philips), and Green Book (CD Interactive).
Recently, some major recording publishers have begun to sell discs that violate the Red Book standard, presumably to make them more difficult to copy. Philips has warned them that including the Compact Disc Digital Audio logo on such non-conforming discs may constitute trademark infringement; either in anticipation or in response, the long-familiar logo is no longer to be seen on many recent CDs. For Germany there exists a database where people are asked to submit their experiences with recent popular Music CDs so that potential buyers are able to preestimate the chance of playing this CD in their PCs, DVD Players, Car radios etc. This project is run by the C't (magazine for Computer Technology) and is called c't-CD-Register.