Computers can store information on various storage media, such as magnetic
disks, magnetic tapes, and optical disks. So that the computer system will
be convenient to use, the operating system provides a uniform logical view
of stored information. The operating system abstracts from the physical
properties of its storage devices to define a logical storage unit, the file. Files are
mapped by the operating system onto physical devices. These storage devices
are usually nonvolatile, so the contents are persistent between system reboots