CD-ROM of Media and Standard

Media
CD-ROMs are identical in appearance to audio CDs, and data are stored and retrieved in a very similar manner (only differing from audio CDs in the standards used to store the data). Discs are made from a 1.2 mm thick disc of polycarbonate plastic, with a thin layer of aluminium to make a reflective surface. The most common size of CD-ROM is 120 mm in diameter, though the smaller Mini CD standard with an 80 mm diameter, as well as numerous non-standard sizes and shapes (e.g., business card-sized media) are also available
Standard
Several formats are used for data stored on compact discs, known as the Rainbow Books. The Yellow Book, published in 1988,[2] defines the specifications for CD-ROMs, standardized in 1989 as the ISO/IEC 10149 / ECMA-130 standard. The CD-ROM standard builds on top of the original Red Book CD-DA standard for CD audio. Other standards, such as the White Book for Video CDs, further define formats based on the CD-ROM specifications. The Yellow Book itself is not freely available, but the standards with the corresponding content can be downloaded for free from