Magnetic Disks and Drives

Magnetic Disks and Drives

Floppy disks are so called because they consist of flexible plastic material which has a magnetizable surface. The surface of a disk is divided into concentric circles or “tracks,” which are then divided into “sectors.” When you insert a blank disk into a drive, it must be formatted before information can be recorded onto it. This means that magnetic areas are created for each track and sector, along with a directory which will record the location of files.

When you save a file, the operating system moves the read/write heads of the disk drive towards empty sectors, records the data, and writes an entry for the directory. Later on, when you open that file, the operating system looks for its entry in the directory, moves the read/write heads to the correct sectors, and reads the file into the RAM area.

Hard disks work in the same way as floppies. However, they have important advantages: they can hold much more data and spin at higher speed, so you can store and retrieve information much faster than with floppies.

Another type of hard drive, known as “removable,” allows you to record data on “cartridges,” which can be removed and stored to be used later. Some systems allow you to back up your entire PC on one disk. Laptops use pocket-sized drives. Digital cameras and music players use micro drives with special cards.

A floppy disk drive spins at 360 rpm (revolutions per minute). A hard disk drive spins at 3,600, 5,400, 7,200, or 15,000 rpm and stores data on a stack of metal rotating disks, called platters.