What is DVD-R?
One of two specifications for recordable Discs is DVD-R (Digital Versatile Disc Recordable), along with DVD+R. Because it is a write-once format, data is forever transferred to the CD and cannot be changed or deleted. More devices can play DVD-R than DVD+R, the older of the two formats. A single-layer DVD-R disc can hold 4.7 GB of data or film, while a double-layer disc has a storage capability of 8.5 GB. A DVD-R disc can only be written to using a suitable DVD-R or Hybrid (DVD-R) optical device. DVD-RW is the name of the rewritable variation of DVD-R.
Both DVD-R and DVD+R DVDs can be written to optically. A coating of heat-sensitive dye on a virgin disc is burned with a sequence of dots by a laser using a DVD-R drive. These areas imprint digital data onto the disc, which a laser in the drive detects and decodes, much like the holes on a professionally-pressed DVD. Both specifications for recordable DVDs have tiny channels that run the length of the disc and direct the laser as it imprints data. On a DVD-R, this groove wobbles at a frequency of 140.6 kHz (as opposed to a much quicker 817.4 kHz on a DVD+R), which guarantees the disc is rotating at the proper pace.
If there is room on the disc even after a DVD-R has been written to once, a drive can still write multiple sessions to add more data. However, when recording to the disc, the DVD-R format employs a less exact tracing technique than DVD+R. A tiny quantity of disc space is lost when starting a new session on a DVD-R because the gap between the two sessions needs to be bigger.