CDlemez

CDlemez, commonly known as a Compact Disc, is a digital optical disc storage format designed to store binary data. It was developed through a collaboration of Sony and Philips and was introduced commercially in the early 1980s for audio playback. The format later expanded to data storage with variants such as CD-ROM for computer data, as well as write-once CD-R and rewritable CD-RW versions. The term CDlemez is often used in Hungarian to refer to these discs.

A standard CDlemez consists of a polycarbonate substrate with a thin reflective metal layer, typically aluminum, and a protective lacquer coating. Data are inscribed as microscopic pits and lands along a spiral track starting near the center of the disc and moving outward. A laser in a CD drive reads the reflected light, where changes in reflectivity encode binary information. The original optical system uses a red or near-infrared laser, with a common reading wavelength around 780 nanometers.

Formats and capacity: The original audio CD standard is defined by what is commonly called the Red Book. CD-ROM also uses the same physical format but stores computer data, defined by the Yellow Book and related specifications. Write-once CD-R and rewritable CD-RW discs use different materials and standards (Orange Book variants). Typical storage capacity is about 650–700 megabytes per standard 120 mm disc, with audio capacity around 74–80 minutes depending on encoding.

Impact and legacy: CDs played a pivotal role in music distribution and early digital data storage, contributing to the decline of vinyl and cassette formats. Although largely supplanted by DVDs, USB drives, and streaming, CDlemez remains in use for archiving, legacy equipment compatibility, and niche applications.