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A spindle with discs of the DVD+RW format

A 12 cm Sony DVD+RW shown in comparison in size to a 7.5 inches (19 cm) pencil.

DVD+RW is the name of a standard for optical discs: one of several types of DVD, which hold up to about 4.7 GB per disc (interpreted as approximately 4.7 × 10⁹ bytes; actually 2295104 sectors of 2048 bytes each which comes to 4,700,372,992 bytes, 4,590,208 binary kilobytes, 4482.625 binary megabytes, or 4.377563476 binary gigabytes) and are used for storing films, music or other data.

DVD+RW supports random write access, which means that data can be added and removed without erasing the whole disc and starting over (up to about 1000 times). With suitable support from the operating system, DVD+RW media can thus be treated like a large floppy disk.

DVD+RW was primarily developed for holding discrete data sets (which change with time) or as recyclable discs for backing up collections of files. However, they (and DVD-RW) are less popular for computer use than DVD-R or DVD+R discs, because they are not suitable for permanent backup files, and because non-rewritable media is significantly cheaper. For similar reasons, rewritable discs are not as widely used for permanent storage of home DVD video recorders as DVD-R and DVD+R.

On the other hand, DVD+RW or DVD-RW make an inexpensive medium for multiple temporary recordings: they can be used for the daily discs of a backup cycle (which are overwritten after a number of days or weeks), and became very popular for their convenience and cheapness as a medium for time-shifting TV (recording programs for a single later viewing and erasing), DVD+RW discs are now playable in three quarters of today's DVD players, many of them Hybrid (DVD±RW) drives.^{[citation needed]}

[edit] Technical details

The recording layer in DVD+RW and DVD-RW discs is a phase change metal alloy (often GeSbTe) whose crystalline phase and amorphous phase have different reflectivity. The states can be switched depending on the power of the writing laser, so data can be written, read, erased and re-written. DVD-R and DVD+R discs use an organic dye.

[edit] History of the DVD+RW standard

The rewritable DVD+RW standard was formalized earlier than the non-rewritable relation DVD+R (the opposite was true with the DVD- formats). Although credit for developing the standard is often attributed unilaterally to Philips, it was "finalized" in 1997 by a coalition of corporations known as the DVD+RW Alliance. It was then abandoned until 2001, when it was heavily revised (in particular, the capacity increased from 2.8 GB to 4.7GB) and commercial products started to arrive (initially, only cheaper and "no-name" recorders) even though the standard was not approved by the DVD Forum (which produced a competing standard, DVD-RW).

However, the "random" rewriting made the DVD+RW format popular. Originally, the branded manufacturers except Philips only made pure DVD-RW recorders and players, but they could not ignore consumer preferences indefinitely.

[edit] See also

• Book type
• DVD+R
• DVD+R DL
• DVD-R
• DVD-RW
• DVD-RAM
• MultiLevel Recording

[edit] External links

• ISO/IEC 17341:2009, Data interchange on 120 mm and 80 mm optical disk using +RW format -- Capacity: 4,7 Gbytes and 1,46 Gbytes per side (recording speed up to 4X) - technical specification
• ISO/IEC 26925:2009, Data interchange on 120 mm and 80 mm optical disk using +RW HS format -- Capacity: 4,7 Gbytes and 1,46 Gbytes per side (recording speed 8X) - technical specification
• Understanding Recordable & Rewritable DVD by Hugh Bennett
• DVD+RW Alliance
• Why DVD+R(W) is superior to DVD-R(W) Also references ADIP (ADdress In Pregroove) + LPP (Land Pre Pit)