Application software can use the directory to find network services and resources. The directory information does not need to be replicated across the network, thereby permitting centralised administration of the network. Traditionally, disks have a magnetic surface that is erasable, re-writable, and writable. Magnetic type disks are referred to as hard disks, hard drives, fixed drives, winchesters, or as floppy disks. Hard disks are usually fixed inside the computer, although, removable hard disks can be used for extra storage, or as a backup device.
Floppy diskettes are removable, and have greatly reduced storage compared to hard disks.
DOS Disk Operating System. At one time DOS was a more generic name used to refer to operating systems of computers. Today, it invariably refers to the standard operating system of personal computers. DNS Domain Name System. DNS accomplishes this by organising computers on the Internet through a hierarchy of domains.