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What disc to buy and use
The chief cause of confusion over these shiny, coaster-sized storage discs collectively known as optical media is that they all look the same.
The differences are in the laser technology, which can etch data on discs in various ways, affecting how much information can be stored there and whether the discs can be recorded on once or many times.
The disc type with the fewest formats is the CD. It is suitable for storing data such as documents and photos, as well as digital music and low-resolution video clips. A CD has a capacity of about 700MB, enough for about 400 high-resolution photos or about 140 four-minute songs in the compressed MP3 format. Alternatively, you could create an audio CD of up to 80 minutes.
There are three formats for a CD. The most basic is CD-Rom, where Rom stands for read-only memory, indicating the disc is pre-recorded and cannot be saved to again. This type of disc is used by software companies to distribute programs, although as the size of programs increases, many are turning to DVD now as they can squeeze more onto it.
On a CD-R disc the R stands for recordable, meaning you can record to the disc once. A
CD-RW, where the RW means rewritable, can be recorded over again and again. The data has to be added in a burning session, which means that while you can add data incrementally until the disc is full, it’s not possible to save data to it as you might to a USB key or floppy disk.
To create a CD you need a CD writer. The front of the tray on the player will carry the CD logo and the CD-R or CD-RW symbol. Most recent PCs include a rewritable CD drive, but if you don’t have one an external unit that connects via the USB socket of a PC can be bought for about £25.
DVDs offer far greater capacity and more formats. Large programs are supplied on DVD-Rom, and these discs can’t be recorded to at all. Then there are recordable and rewritable versions that carry an R or RW on their label. These can store around 4.7GB of files, providing space for about 2,000 photos or a couple of hours of high-quality digital video.
The key difference with DVDs is denoted by a plus (+) or minus (-) symbol, which indicates which format they are compatible with. This is necessary because two versions of recordable DVDs were invented by different firms.
Basically a DVD format name is split into three parts. Taking DVD-RW as an example, the DVD indicates that it is a DVD, the - means it is in the minus format and the RW shows that it can be recorded to multiple times. Some DVD drives carry the symbol +/-, which means that they can read or create discs in both formats. External DVD burners can be purchased for roughly £40.
Another DVD option is double-layer discs and drives, sometimes called dual layer. On such discs there is a second layer in the surface dye. This means more data can be stored on the disc, up to about 8.5GB in total.
Double-layer discs only come in record-once DVD-R and DVD+R versions. The high capacity of regular and double-layer DVDs means they are suitable for storing lots of high-quality video.
A less well-known member of the DVD family is DVD-Ram. The minus symbol in the name does not indicate a format. Ram stands for random access memory. This disc can be saved to like a USB key. DVD-Ram drives are rare in PCs, but are common in DVD video recorders and camcorders.
The Wizard3, 15/12/08, 13:02