DVD-R and DVD-RW
DVD-R and DVD-RW are also both formats of the DVD Forum. Both formats generally use 4.7 GB discs, although some professional DVD-R drives use 3.95 GB discs.
DVD-R is a write-once recordable format which allows excellent compatibility with both standalone DVD players and DVD-ROM drives. There are two main types of DVD-R discs: DVD-R for General Use and DVD-R for Authoring. Most consumer DVD-R burners use the cheaper General Use discs, while some professional burners use Authoring discs. The correct media type appropriate for the recorder must be used when burning a DVD-R. However, once written, the discs should be readable in either drive type. (General Use DVD-R is designed to prevent backup of encrypted commercial DVDs.)
DVD-RW media uses rewriteable discs which are rated for more than 1000 rewrites in ideal situations. The majority of standalone DVD players will play video recorded on DVD-RW discs, but the compatibility is not as high as with DVD-R.
Current DVD-RW recorders also record to DVD-R. However, the reverse was not always true. Some older DVD-R recorders were not capable of writing to DVD-RW discs (although some were able to read DVD-RW discs burned with other drives).
DVD-RW and DVD-R have heavy penetration into the professional multimedia market as well as the general consumer market. For instance, the Apple SuperDrive, found in many pro and consumer Mac computers, is simply a DVD-R/DVD-RW (and CD-R/CD-RW) capable burner.
DVD+R and DVD+RW
These two formats are backed by the DVD+RW Alliance. While these formats are not supported by the DVD Forum, several members of the DVD+RW Alliance are also members of the DVD Forum. These discs are very similar to DVD-R and DVD-RW in design, usage, and compatibility.
DVD+RW, like DVD-RW, is a rewriteable 4.7 GB format, and overall it has similar functionality to DVD-RW. The level of compatibility of standard DVD+RW discs in standalone DVD players is similar to that of DVD-RW. The rewritability of DVD+RW is also said to be similar to that of DVD-RW, allowing up to 1000 rewrites.
One potential advantage of the DVD+RW format is Mount Rainier (DVD+MRW) drag-and-drop file access support planned for Longhorn, a future version of Windows slated for release in 2005. Older DVD+RW drives do not support this function, but newer drives may. While DVD+MRW is arguably not as robust a data solution as DVD-RAM, DVD+MRW potentially will offer higher read compatibility in current DVD-ROM drives.
DVD+R is a format that was introduced to consumers in early 2002. The first generation +RW recorders did not support DVD+R recording, and likely cannot be upgraded to do so. However, all current models of DVD+RW recorders also support DVD+R recording. Compatibility of +R discs in standalone DVD players is similar to that of DVD-R.