Operating System takes help from device drivers to handle all I/O devices. Device driver:It is a computer program that operates or controls a particular device attached to a computer or automaton. It provides a software interface to hardware devices, enabling operating systems and other computer programs to access hardware functions without knowing precise details about the hardware being used. A device driver is generally written by the device's manufacturer and delivered along with the device on a CD-ROM. The main purpose of device drivers is to provide abstraction by acting as a translator between a hardware device and the applications or operating systems that use it. Programmers can write higher-level application code independently of whatever specific hardware the end-user is using. For example, a high-level application interacting with a serial port may have "send data" and "receive data" functions. A device driver implementing these functions would communicate to the particular serial port controller installed at a lower level on a user's computer. Additional Information A disk compression software utility increases the amount of information that can be stored on a hard disk drive of a given size. Universal Serial Bus (or USB) Port can connect all kinds of external USB devices such as external hard disks, printers, scanners, mouse, keyboards, etc. It was introduced in 1997. Most computers provide two USB ports as a minimum. Disk defragmentation helps rearrange the files on the disk to contiguous spaces and thus improve disk performance.