There are basically two types of disk storage for computers: magnetic and optical. Magnetic storage is represented by the standard floppy and hard disks installed in most PC systems, where the data is recorded magnetically on rotating disks. Optical disc storage is similar to magnetic disk storage in basic operation, but it reads and records using light (optically) instead of magnetism. Although most magnetic disk storage is fully read and write capable many times over, ma by optical storage media are either read only or write once. Note the convention in which we refer to magnetic as disk and optical as disc. This is not a law or rule but seems to be followed by most in the industry.
Some media combine magnetic and optical techniques, using either an optical guidance system (called a laser servo) to position a magnetic read/write head (as in the LS-120/LS-240 Super Disk floppy drive) or a laser to heat the disk so it can be written magnetically, thus polarizing areas of the track, which can then be read by a lower-powered laser, as in magneto-optical (MO) drives.
The most promising development in the optical area is that CD-RW (compact disc-rewritable) or DVD+RW (DVD + rewritable) drives with Easy Write (Mount Rainier) support are starting to replace the venerable floppy disk as the de facto standard, interchangeable, transportable drive and media of choice for PCs. In fact, some would say that has already happened. Most new systems today include a CD-RW drive, and some also include some type of rewritable DVD drive. Even though a floppy drive is also included with most systems, it is rarely used except for running tests; running diagnostics; or doing basic system maintenance, disk formatting, preparation for OS installation, or configuration.
Optical technology standards for computers can be divided into two major types:
* CD (CD-ROM, CD-R, CD-RW)
* DVD (DVD-ROM, DVD-RAM, DVD-RW, DVD-R, DVD+RW, DVD+R)
The CD and DVD storage.