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Professional Windows® Embedded Compact 7 by Thierry Joubert, David Jones, Samuel Phung

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WHAT IS A DEVICE DRIVER?

A componentized operating system such as Windows Embedded Compact enables you to customize an embedded operating system by selecting only those drivers and applications that are needed and relevant. This enables you to make a smaller footprint.

When you add new hardware to a computer system, the operating system can’t use it until a suitable device driver is loaded for it. The system searches for a driver from a list of available drivers, and if found the system loads the driver; otherwise, you need to download or install the driver from media supplied with the hardware.

A device driver provides an interface between the operating system and the device and handles the transfer of data between the two. It also manages the configuration of the device and reads its status. For example, a serial port driver moves data from the port’s receive data register upon reception to a software buffer that applications can use. It places data in the transmit register when an application sends data, enabling the hardware to handle the transmission from there. Operating system calls to the driver configure such things as the baud rate and number of stops bits for the port. An application can check the status of the port through operating system calls to the driver.

A device driver provides input/output (I/O) through ports written to and read from by the device driver. The device driver manages the functional configuration of the device and checks its status. Finally, the ...

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