Driver
In the context of computing, a driver is a program that controls a device. It accomplishes this control by acting as a communications translator. In other words, a driver mediates the communication between the particular device and the programs that use that particular device. Each device has its own commands that are recognized only by the driver. By contrast, most programs that utilize devices do so using generic commands. The driver functions to accept the generic commands from a program and then to translate these commands into the specialized commands recognized by the device.
By isolating the codes for a device in the particular driver and having a consistent interface between the driver and the device, adding a new device is easier. For example, if a printer is replaced, the operating system is not affected; only the information in a new driver need be installed. Examples of devices that utilize a driver are a printer, disk drive, CD-ROM, speakers, modem, mouse and a keyboard. Each of these devices requires its own driver in order to function.
Drivers also serve a power related function. Modern computers are designed to operate on low power levels--battery operation is a commonplace feature. Peripheral devices, however, often demand higher power for their operation. A device driver can boost the low power from the microprocessor to meet the power needs of the device.
Some drivers come as part of the computer's operating system. A keyboard driver is an example. Other devices, such as a new printer, require the loading of a new driver during the installation of the device.
Driver program files can be distinguished from other system files based on their file extensions. In DOS systems, driver files have a .sys extension, whereas in Windows operating environments, drivers typically have a .drv extension.
The UNIX operating system utilizes several different types of device drivers: block device drivers, character device drivers, network device drivers, and so-called pseudo-device drivers. A block device driver facilitates the back-and-forth flow of information between the computer and the device. Disk drives commonly utilize a block driver. A character device driver is used for a device such as a line printer that handles one character at a time or small blocks of character information at a time. A network device driver connects a subsystem of a network to the main network. Finally, a pseudo-device driver does not control a physical piece of hardware. Rather, it emulates such control in order to control a process such as a remote login.
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