Optical Drive Plus and Minus

In each line the + or the - has other meanings.

For CD and BD it is just a dash, separator to add sections of the standard to which the drive complies.

For DVD it is a different story.

You need to know the story of the creation of DVD to understand it.

DVD is created from the need the Pentagon had for data storage. To achive the best system they called in all the companies which had research on data storage and typically optical storage.

DVD stands for Digital Versatile Disk, and is organised as an hard disk, where CD is organised as an older analog audio vinyl disk.

Philips and Sony only joined to make sure that the older CD patents were respected.

Sony was already working on the BD and Philips was only interested in a recordable version the format, which was not what the other companies wanted.

Philips worked out the +R and +RW standards which made sure that each recorded disk could be read by each DVD player already made. (DVD should not be added as this is not supported by the DVD consortium)

But the DVD consortium refused this standard (contained to much patents only held by Philips) and worked out the DVD-R and DVD-RW standard which only wanted the recorded disk to be played in a recorder. (thus you could not record a disk for you neighbour)

They even build in +R/W detection algoritms to refuse such a disk in their players.

Others in the consortium had already the DVD-RAM, and wanted this to be the recording standard, cutting all links with the already sold DVD players.

It turned out that some players saw that the only way out was the creation of multi format player, Sony on top as they only wanted DVD to remain scattered (to have no competition with the BD), to which the contestants complied very soon.

The difference is in how you need to follow the non written track on the disk and how the adressing and closing of the disk is realised.