methods of data storage

Data storage is the holding of data in an electromagnetic form for access by a computer processor. There are two main kinds of storage:

Primary storage is data that is held in in random access memory (RAM) and other memory devices that are built into computers.

Secondary storage is data that is stored on external storage devices such as hard disks, tapes, CD's.

---

The table below summarises the main methods of data storage

Method	Commentary
Hard disks	Often called a disk drive, hard drive or hard disk drive, this method of data storage stores and provides relatively quick access to large amounts of data. The information is stored on electromagnetically charged surfaces called 'platters'.
Floppy disks	A floppy disk is a type of magnetic disk memory which consists of a flexible disk with a magnetic coating. Almost all floppy disks for personal computers now have a capacity of 1.44 megabytes. Floppy disks are readily portable, and are very popular for transferring software from one PC to another. They are, however, very slow compared to hard disks and lack storage capacity. Increasingly, therefore, computer manufacturers are not including floppy disk drives in the products as a built-in storage option.
Tape storage	Tape is used as an external storage medium. It consists of a loop of flexible celluloid-like material that can store data in the form of electromagnetic charges. A tape drive is the device that positions, writes from, and reads to the tape. A tape cartridge is a protectively-encased tape that is portable.
Optical disks	An optical disc is a storage medium that can be written to and read using a low-powered laser beam. A laser reads these dots, and the data is converted to an electrical signal, finally converted into the original data.
CD-R	Compact Disc-Recordable ("CD-R") discs have become a universal data storage medium worldwide. CD-Rs are becoming increasingly popular for music recording and for file storage or transfer between personal conmputers. CDR discs are write-once media. This means that - once used -they cannot be erased or re-recorded upon. CD-R discs can be played back in any audio CD player or CD-ROM drive, as well as many DVD players and drives.
CD-RW	Compact Disc-Rewritable (CD-RW) disks are rewritable and can be erased and re-recorded upon over and over again. CD-RW discs can only be used on CD players, CD-ROM drives, and DVD players and drives that are CD-RW playback-compatible.
DVD	A DVD (Digital Versatile Disc or Digital Video Disc) is a high density optical disc with large capacity for storage of data, pictures and sound. The capacity capacity is 4.7 GB for single sided, singe layer DVD disc - which is approximately 7 times larger than that of a compact disc.