Hard Drive

A hard-disk or a hard drive has become an inseparable part of any server or computer. A supercomputer or mainframe has hundreds of such drives. Apart from computers, many devices such as VCRs, camcorders and gaming consoles too use hard drive. The key function of any hard drive is to store digital data. This allows the stored data to be recalled even after the computer is shut down. Invented in 1950s, the first hard disks measured 20 inches with an ability to store a few megabytes. The key difference between a floppy disk and a hard drive is that the hard drive has a hard platter that holds the magnetic medium; whereas, the floppy is inbuilt with flexible plastic film.

Hard drives use magnetic a recording technique similar to any tape. This magnetic field can be easily erased and rewritten. Generally, a desktop machine has a hard disk capacity varying from 10 to 200 GB. The data is stored in files, which are collection of number of bytes. The performance of the hard disk is measured in two parameters: data rate and seek time. Data rate refers to the number of bytes that a hard drive can transfer to CPU and seek time is the time taken to transfer. The seek time may vary form 10 to 20 (or more) milliseconds.