Compact Disc

Compact Disc

The Compact Disc (CD) is a digital optical disc data storage format that was co-developed by Philips and Sony and released in 1982. The format was originally developed to store and play only sound recordings (CD-DA) but was later adapted for storage of data (CD-ROM). Several other formats were further derived from these, including write-once audio and data storage (CD-R), rewritable media (CD-RW), Video Compact Disc (VCD), Super Video Compact Disc (SVCD), Photo CD, PictureCD, CD-i, and Enhanced Music CD.

History

The Compact Disc was developed to replace the vinyl record and cassette tape as the primary medium for audio recordings. The project began in the late 1970s, with Philips and Sony collaborating to create a new digital audio disc. The first commercial CD player, the Sony CDP-101, was released in October 1982.

Technical Specifications

A standard CD is 120 mm in diameter and 1.2 mm thick, with a 15 mm center hole. The disc is composed of a polycarbonate plastic substrate, a reflective metallic layer, and a protective lacquer coating. CDs are read by a 780 nm wavelength semiconductor laser.

Data Encoding

CDs use a digital encoding format known as PCM to store audio data. The audio is sampled at 44.1 kHz with a 16-bit resolution, which provides a frequency response of 20 Hz to 20 kHz and a dynamic range of about 96 dB.

Capacity

A standard CD can hold up to 74 minutes of audio or approximately 650 to 700 MB of data. This capacity is achieved by encoding data in a spiral track that starts at the center of the disc and extends outward.

Variants

• CD-ROM: A Compact Disc used to store data for access by a computer.
• CD-R: A recordable CD that can be written once and read many times.
• CD-RW: A rewritable CD that can be written, erased, and rewritten multiple times.
• VCD: A format for storing video on a CD.
• SVCD: An enhanced version of VCD with better video quality.

Impact and Legacy

The introduction of the Compact Disc revolutionized the music industry by providing a more durable and higher quality format than vinyl records and cassette tapes. CDs quickly became the dominant format for music distribution in the late 1980s and 1990s.

Decline

With the advent of digital downloads and streaming services in the 2000s, the popularity of CDs began to decline. However, they remain a popular format for audiophiles and collectors due to their physical nature and perceived sound quality.

See Also

• DVD
• Blu-ray Disc
• Optical disc

References

• "The Compact Disc Story," Philips Research.
• "The History of the CD - The Beginning," Sony Corporation.

External Links

• Philips Official Website
• Sony Official Website