DVD – Digital Video Disk – optical disk for storing videos, audio files and archive data. It uses a 120mm (4.7 inches) diameter platter. It was invented in 1995 in Japan and can store more data than the preceding CD (Compact Disk) format; up to 4.7 GB in standard format – single-layer and single-sided, 8.5 GB with a dual-layered, single-sided disk, and up to 17.08 GB in an extended double-sided, double-layer format.
DVD-R and DVD+R can have data written to them by a DVD recorder, becoming DVD-ROMs which are read-only disks.
DVDs are written and read using a 650nm red laser, which is focused to different depths in a dual-layer disk.
DVDs can spin at up to 3,2000 rpm, faster than CDs at 2,300rpm.
The Blu-ray optical disk format, released in 2006, replaced DVDs, as dual layer Blu-ray disks, with their 405nm blue laser, have a much higher capacity; up to 50 GB.
