Net Terms Device Driver A device driver is a program that controls a particular type of device that is attached to your computer. Essentially, a device driver converts the more general input/output instructions from your computer's operating system into messages that the device can understand. There are device drivers for printers, monitors, CD-ROM and DVD drives, modems, and so on. When you buy an operating system (such as Windows 95 or OS/2), many device drivers are already built into that system to recognize certain products. However, if you later buy a new type of device that the operating system didn't anticipate or doesn't understand, you'll have to install a new device driver for it to function properly.