Most CD-rewritable drives copy data at a ratio of about eight to one, meaning that they can record about 60 minutes of music (or 545 megabytes of data) onto a compact disc in about 7 1/2 minutes.
Copying data onto rewritable discs (CD-RW), an increasingly popular option for people who want to back up their data, is slightly slower, although the veloCD still copies data on a rewritable disc in about half the usual time.
These materials are in fact commonly used as the data layer in rewritable compact disks and digital versatile disks (CD-RW and DVD-RW) where the change in optical properties is exploited to store data.
Because their optical properties change with these states as well, they have also proved useful in data storage, such as rewritable DVDs.
EPROM (erasable programmable ROM), EAROM (electrically alterable ROM), and flash memory are types of nonvolatile memories that are rewritable, though the rewriting is far more time-consuming than reading.
Q. Can you play DVD-RAM discs on a regular DVD player? A. DVD-RAM, a rewritable format and is often used for data backups, is one of the many available formats for DVD discs in a family that also includes DVD-R, DVD+R, DVD-RW and DVD+RW.
CD-RW's, rewritable CD's that let you copy and recopy data to the disc, have a shorter life expectancy than CD-R's: about 30 years.
Many small-business customers now use rewritable CDs and portable hard disks to back up their data.
These double-density discs still won't hold as much as rewritable DVD discs, which can store almost 5 GB of data.
To store data, I have used floppy disks, diskettes, zip discs, rewritable CDs, flash drives, burnable DVDs, even the Commodore Datasette.
