DVD

A DVD is an optical disc used to store digital data. The term stands for "Digital Versatile Disc" or "Digital Video Disc". The disc is approximately 12 centimetres in diameter, the same as a CD, but has significantly greater storage capacity.

Reading and writing are performed by a laser beam that strikes the surface of the disc. Small indented areas (pits) and flat areas (lands) on the surface represent the data. Because a DVD uses a shorter-wavelength laser than a CD, data can be written to much smaller spaces, which increases storage capacity.

History

The DVD was developed in the mid-1990s, when major electronics manufacturers from Japan and Europe agreed on a single global standard after two competing projects had been released. A standards body, the DVD Forum, was established to oversee the technology specifications. It entered the mass market in the late 1990s and early 2000s, replacing VHS cassettes.

Storage capacity and types

The most common type, single-layer and single-sided, holds approximately 4.7 gigabytes. Double-layer versions exist that hold up to three additional gigabytes, and both sides can be used. By application, there are DVD-ROM (read-only), DVD-R and DVD+R (write-once), and DVD-RW and DVD+RW (rewritable).

Video use

DVD Video uses MPEG-2 compression to store a full film on a single disc. Multiple audio languages, subtitles, and interactive menus can be included. The format also incorporates copy protection and a region code system that restricts where a disc can be played.

Current status

DVD use has declined since the arrival of Blu-ray, internet storage, and streaming services. It remains in use for backup storage, software distribution, and film libraries. Some newer computers no longer include disc readers.