Compact disc

Background

The compact disc was co-developed by Philips and Sony to store and play digital audio recordings, using the Compact Disc Digital Audio (CD-DA) standard. First released in Japan in October 1982, it was the second optical disc format to reach the market, after the LaserDisc. The technology was later adapted for computer data storage as CD-ROM and expanded into writable formats such as CD-R and CD-RW, as well as multimedia formats like Video CD and Super Audio CD. By 2007, over 200 billion CDs had been sold worldwide.

Standard CDs have a diameter of 120 mm and typically hold up to 74 minutes of audio or 650 MiB of data, later extended to 80 minutes or 700 MiB by reducing track spacing. Smaller variants, such as the Mini CD, range from 60 to 80 mm in diameter. The CD is made from 1.2 mm thick polycarbonate plastic, with a reflective layer of aluminum or gold protected by lacquer. Data is encoded as pits and lands in a spiral track, read by a 780 nm semiconductor laser.

The CD gained widespread popularity in the late 1980s and early 1990s, surpassing the phonograph record and cassette tape in U.S. sales by 1991. By 2000, CDs accounted for 92.3% of the U.S. music market share. It is widely regarded as the final dominant format of the album era, before the rise of MP3, digital downloads, and streaming platforms in the mid-2000s led to its decline.