How drivers work -done by Jiangkuo.

Jiangkuo has some problem with the use of the blog so I help him to post.
A device driver is a component that Windows uses to interact with a hardware device, such as a modem or network adapter. Rather than access the device directly, Windows loads device drivers and calls functions in the drivers to carry out actions on the device. Each device driver exports a set of functions; Windows calls these functions. The driver functions contain the device-specific code needed to carry out actions on the device. Drivers are signed by Microsoft after they pass a series of tests for functionality and reliability. For a driver to earn this certification, it must pass a series of tests administered by the Windows Hardware Quality Labs (WHQL). Due to stringent WHQL standards, using signed drivers typically results in a more stable system.
Microsoft digitally signs drivers that pass the WHQL tests and Windows Server 2003 performs signature detection for signed drivers for various device types, which include the following:
Keyboards
Hard disk controllers
Modems
Mouse devices
Multimedia devices
Network adapters
Printers SCSI adapters
Smart card readers
Video adapters

The above figure shows how device drivers operate in both kernel mode and user mode.
The Types of Device Drivers

There are many types of device drivers, some of which are specific to certain machines. For example, device drivers for laptop computers are proprietary and installed by the manufacturer upon being designed. A desktop is typically the exact opposite. If the hard drive on a laptop is reformatted or deleted for any reason, all the original drivers will remain intact. With a desktop computer, you are generally required to visit the websites of each individual manufacturer, download and reinstall the drivers along with another operating system.

When Good Drivers Go Bad

There may be instances when device drivers do not function as intended or have conflicts with other computers. You will find that manufacturers make improvements to device drivers similar to how software developers upgrade programs. In some cases, such upgrades can make older drivers obsolete. Likewise, an updated driver can heal a wide range of bugs and behavior problems endured by a particular device. For example, if your printer isn't functioning properly, fixing the issue is often as simple as checking the manufacturer's website and downloading the corresponding driver.

How Device Driver Updates Work

Device drivers download like any other program and typically act as self-installing files. Most of them download as exe. or executable files. In most cases, you simply need to click on the file and the installation program is launched. The program will usually scan the system first to ensure that the driver corresponds to the installed hardware component. A device driver can often be installed in a matter of seconds, but normally requires a system reboot in order to function properly with the corresponding hardware.

The easiest way to check the status of device drivers on a Windows operating system is to access the Device Manager utility. Simply right-click the "My Computer" icon, select "Properties," click on the "Hardware" tab, and then choose "Device Manager." Once you are in the Device Manager window, highlight the hardware device you want to investigate and right-click it. In the new window, select "Properties" and click on the "Driver" tab. From here, you can view the name of the driver, the version number, as well as perform the necessary updates.