The worker dispatched from the manufacturer of a peripheral device. He is responsible for communication and data transfer between the peripheral device and the computer. Whenever the operating system or application program wants to use the functions of the device, the driver manipulates the device, and moves data and control signals between the memory and the device.

Even though the operating system is the general manager of the computer, it is impossible for OS to recognize all the computer peripherals in the world. There are many devices that were developed or launched after the operating system developed. Even if these devices are connected to the computer system with appropriate cables, OS cannot understand the electronic signals sent from them, and they can only be classified as "unknown devices". How can these devices be recognized by the computer and function properly? The answer is for the manufacturer of a peripheral device to provide the software called "device driver" as the contact window between OS and the peripheral device.

The device driver is like a dispatched employee of the device manufacturer stationed in the operating system. A device driver has two main tasks: first, to answer the operating system's regular inquiries, so that the operating system can correctly identify the name and classification of the device, then categorizes it into the correct department. And second, when the system or an application program wants to use the function of the device, the driver transfers the input/output data and control signals between the memory used by the program and the device, via the data transfer channel specified by the operating system. So that the device can be properly functioning at the right corner in the system.

Even a peripheral device is recognized by the operating system without a device driver, OS still needs the driver from the manufacturer, otherwise it can only be used at a minimum level. Take a graphics card for example, when a graphics card is installed in a dedicated slot in the computer system, the system certainly knows that it's a graphics card, and so the screen can be viewed on the computer screen, but only the lowest resolution is displayed without any acceleration and functions from the GPU. The operation system and game programs can only use the wonderful features of the GPU after the driver from the manufacturer is installed.