A compact disc can contain several different kinds of information. Many compact discs appear to be very similar to other forms of permanent storage such as hard or floppy disks. CD-ROM (Compact Disc - Read Only Memory) refers to a file format used for compact discs containing data that can be read by a computer's file system. This format is also known as Yellow Book. Yellow Book refers to the specification published by Philips Consumer Electronics Company and Sony Corporation that describes the physical layout of the CD-ROM disc format. This document evolved into the ISO (International Organization for Standardization) 9660 standard.
Another form of compact disc data is Compact Disc Digital Audio (CD-DA) and is also known as Red Book. This format is used for compact discs containing digital audio. CD-DA discs are encoded as 16-bit stereo PCM (Pulse Code Modulation) at 44.1 kHz. See Waveform Data Formats for more information on this recording method.
For every second of CD-DA audio data, 172KB of disc storage is required. Therefore, the sustained data rate required to play back a selection from a CD-DA track is 172KB per second. The CD-DA track format typically has an error recovery rate of 90 percent. A 10 percent error rate is acceptable for audio discs, because errors that escape the correction mechanism are usually compensated for by audio filters in the CD player hardware.
Unlike CD-DA data, information stored in a CD-ROM file system cannot tolerate such a relatively high error rate. As a result, CD-ROM format data is transferred to an application at an apparent data rate of 150KB per second. The lower data rate results from the additional error correction bits utilized by the file system to produce an acceptable error rate.