DVD and CD formats explained

There are two major versions of recordable DVD: DVD-R and DVD+R, which were developed by different companies and are not compatible with each other.

However, most modern DVD writers will read and write both types of disc. For older writers, take note of which version the device supports before buying discs.

Both can store 4.7GB of data, as can their rewritable equivalents – DVD+RW and DVD-RW.

Again, most modern writers will write all four of the above formats.

Until recently, double-layer discs with up to 8.5GB of space, were found only in shop-bought film discs, but now most new DVD writers on sale will write DVD+R double-layer and DVD-R double-layer discs.

These writers are no more expensive than others, but the discs are more expensive than standard ones and, of course, the disc will take longer to write, having twice as much data on it.

DVD-Ram (Ram stands for random access memory, a jargon term for storage that can be written to many times) discs, on the other hand, are not widely used in computers, and are mainly found in DVD video recorders and camcorders.

Some PC writers can write these discs, but most cannot write or read DVD-Ram discs.

DVD-Ram discs usually come in a plastic housing that protects the surface of the disc. Manufacturers think that even DVDs are not enough for future needs, so two competing formats, Blu-ray and HD-DVD, are being developed.

Blu-ray discs will store up to 54GB (eight hours of super-high-quality video) and HD-DVD will store up to 30Gb (four hours of similar video).

Which disc is right for your PC?
It may not be easy to figure out which discs will work in your PC. If you are buying a new PC, take a close look at the specifications or feature list, which will list the optical reader/writer and which formats it supports. If it does not, ask the retailer or manufacturer.

All CD writers on sale will read both CD-R and CD-RW discs, as well as standard CDs and CD-Roms, and all DVD writers on sale should be able to read both DVD-R/RW and DVD+R/RW, as well as standard DVDs and DVD-Roms.

If you already own the PC, take a look at the front of the computer. On the writer there will probably be several symbols – the compact disc logo, which will usually say ‘recordable’ or ‘rewriteable’ underneath if it is capable of those, and possibly one or more DVD logos.

There may be up to three: one for DVD-Rom reading, one for DVD+R/RW writing, and one for DVD-R/RW writing.

Remember that these abbreviations contain three pieces of information: the disc type, format and capability.

For example, in DVD-R/RW, the ‘DVD’ means it’s a DVD, the symbol indicates it is the minus format, and ‘R/RW’ means the disc drive can read and record data to the disc many times.

You may also spot the use of ‘+/-’ on a drive and this means it supports both plus and minus formats. This is also often referred to as a multiformat writer.