A device driver is a program that controls a particular type of device that is attached to your computer. It consists of software code that allows your PC's operating system to interact with a hardware device. Every device driver performs a different function due to the fact that there are so many peripheral devices that connect to your PC's operating system. Peripheral devices are devices such as printers, hard drives, scanners and keyboards. The device driver provides a way for your PC to communicate with the peripheral device.
How does a device driver work?
For example, let's say you want to print a document to your printer. Windows accesses the Function Dispatch Table for the function code required to carry out this task. It then sends a request to the appropriate device, in this case your printer. Requests are called IRPs or Input/Output Request Packets. When the printer driver receives and IRP, it does one of three things: it either understands and does its function followed by sending a confirmation notice that the job is complete; it accepts the request and places it in a queue (if the device is busy doing something else); or it notifies Windows that there's a problem and it cannot perform the request.
Generally, device drivers operate in a mode called "kernel" mode. Windows handles program codes in either user or kernel mode. User mode is typically used for programs. When using user mode, programs can call and use services provided by the operating system but cannot access the hardware directly. Processes running in kernel mode can interact with system memory and hardware.
Advice about device drivers
Like computer programs, device drivers and hardware can cause computer crashes and instability which needs to be fixed by replacing or updating a device driver sometimes to solve the computer and hardware problems. Therefore, it is important to note that before you install a device driver it is a good idea to check the website of the manufacturer for the peripheral device to make sure that you have the right driver updates available.
You can also check to see if the driver has been digitally signed by Microsoft which means the driver has been approved by Microsoft for compatibility with the Windows operating system. You can check the signature by clicking on "Start" on your main toolbar on the desktop and then clicking on "Run." Type "sigverif" into the command prompt to run a scan of all of your device drivers and to verify which drivers contain signatures.