CD Media, DVD Media, Tape Media
CD-ROM (which stands for "Compact Disc read-only memory") is a Compact Disc (CD Media) that contains data accessible by a computer. While the Compact Disc format was originally designed for music storage and playback, the format was later adapted to hold any form of binary data. CD-ROMs (including CD R and CD RW) are popularly used to distribute computer software, games, multimedia content, MP3, and much more, though any data can be stored (up to the capacity limit of a disc). Some CDs hold both computer data and audio with the latter capable of being played on a CD player, while the data (such as software or digital video) is only usable on a computer (with CD-ROM or DVD drive). These are called Enhanced CDs. Prerecorded CD-ROM discs are identical in appearance to audio CDs, and data is stored and retrieved in a very similar manner (only differing from audio CDs in the standards used to store the data). Discs are made from a 1.2 mm thick disc of polycarbonate plastic, with a thin layer of aluminum to make a reflective surface. The most common size of CD-ROM disc is 120 mm in diameter, though the smaller Mini CD standard with an 80 mm diameter, as well as numerous non-standard sizes and shapes (e.g. business card-sized media) are also available. Recordable formats, such as CD-R and CD-RW allow a computer to record directly on the CD.
Another variation on the CD is the DVD, and is the most popular optical disc storage media format for movies. Its main uses are video and data storage. Most DVD Media are of the same dimensions as compact discs (CDs) but store more than 6 times as much data. Variations of the term DVD often describe the way data is stored on the discs: DVD-ROM has data which can only be read and not written, DVD R (DVD-R and DVD+R) can be written once and then functions as a DVD-ROM, and DVD RW (DVD-RAM, DVD-RW, or DVD+RW) holds data that can be erased and thus re-written multiple times. DVD-Video and DVD-Audio discs respectively refer to properly formatted and structured video and audio content. Other types of DVD discs, including those with video content, may be referred to as DVD-Data discs. The term "DVD" is commonly misused to refer to high definition optical disc formats in general, such as Blu-ray and HD DVD. CDs & DVDs are made by a number of manufacturers, including: Philips (Hotan), Imation, JVC, Maxell, Memorex,
A floppy disk (or floppy diskette) is an older data storage medium, that has been around since the 1970s, that is composed of a disk of thin, flexible ("floppy") magnetic storage medium encased in a square or rectangular plastic shell. Floppy disks are read and written by a floppy disk drive or FDD, the initials of which should not be confused with "fixed disk drive", which is another term for a hard disk drive. Invented by IBM, floppy disks first were introduced in 8" size, then 5.25" became popular with the Atari, Commodore, and PC, and the successor 3.5" formats enjoyed many years as a popular and ubiquitous form of data storage and exchange, from the late 1980s to the late 1990s. However, they have now been largely superseded by flash and optical storage devices while e-mail has become the preferred method of exchanging small to medium size digital files. Storage of floppies was always one of the greater challenges of using this media.
Tape Media is mostly used now just for backup purposes, and generally on network servers, and is not so different from a video cassette. The DAT tape format is the most popular now, but in the past almost every conceivable tape format was introduced. Digital Data Storage (DDS) is a format for storing and backing up computer data on magnetic tape that evolved from Digital Audio Tape (DAT) technology, which was originally created for CD-quality audio recording. In 1989, Sony and Hewlett Packard defined the DDS format for data storage using DAT tape cartridges.