Hard Disk

The hard disk is a direct-access storage medium with a rigid magnetic disk. The data is stored as magnetized spots arranged in concentric circles (tracks) on the disk. Each track is divided into sectors. The number of tracks and sectors on a disk is known as its 'format'.

The disk rotates at a high speed (about 3,600 rpm). As the disk rotates, read/write heads move to the correct track. The storage capacity of a hard disk can be Gigabytes (Gb), i.e. thousands of Megabytes (1000Mb), of information.

Magnetic Tape

A recording medium consisting of a thin tape with a coating of a fine magnetic material which is used for recording analog or digital data. Data is stored in frames across the width of the tape. The frames are grouped into blocks or records which are separated from other blocks by gaps.

Magnetic tape is a serial access medium, similar to an audio cassette, and so data (like the songs on a music tape) cannot be quickly located. However large amounts of information can be stored within magnetic tape. This characteristic has prompted its use in the regular backing up of hard disks.

Floppy Disk

A floppy disk is a thin magnetic-coated disk contained in a flexible or semi-rigid protective jacket. Data is stored in tracks and sectors.

The floppy disks are 3.5" in size. Older floppy disks 5.25" in size may also be in use. Double-sided high density 3.5" disks can hold 1.44 Mb of data.

Once data is stored on a floppy disk, it can be 'write protected' by clicking a tab on the disk. This prevents any new data from being stored or any old data from being erased.

Optical Disk / Compact Disk/DVD

An optical disk is impressed with a series of spiral pits in a flat surface. A master disk is burned by high-intensity laser beams in bit-patterns from which subsequent copies are formed which can be read optically by laser. The optical disk is a random access storage medium. Information can be easily read from any point on the disk. A standard CD-ROM can store up to 650Mb of data with 14,500 tracks per inch (tpi).

CD-ROM stands for Compact Disk - Read Only Memory. It is now possible to have CD-ROMs where extra tracks of information can be written onto them by the user. These are called read/writable CD-ROMs and these are becoming a popular and cheap method for storage.

DVD also known as "Digital Versatile Disc" or "Digital Video Disc" is an optical storage media format that can be used for data storage, including movies with high video and sound quality. DVDs resemble Compact disks because their diameter is the same (120 mm or 4.72 inches, or occasionally 80 mm or 3.15 inches), but they are encoded in a different format and at a much higher density.

USB Flash Drive

USB flash drives are NAND-type flash memory data storage devices integrated with a USB (universal serial bus) interface. They are typically small, lightweight, removable and rewritable. Capacity is limited only by current flash memory densities, although cost per megabyte may increase rapidly at higher capacities due to the expensive components. (USB Memory

Memory card readers are also available, whereby rather than being built-in, the memory is a removable Flash memory card housed in what is otherwise a regular USB flash drive.

USB flash drives offer potential advantages over other portable storage devices, particularly the floppy disk. They are more compact, generally faster, hold more data, and are more reliable (due to both their lack of moving parts, and their more durable design) than floppy disks. ws.

When the user plugs the device into the port, the computer's operating system recognizes the device as a removable drive and assigns it a drive letter.

Punched Tape

Punched tape is an old-fashioned form of data storage. It consists of a long strip of paper in which holes are punched to store data. Punched tape was first developed as a way of storing messages for teletypewriters. The idea was to type in the message to the paper tape, and then send the message at "high speed" from the tape.