PPT Slide
 
 
What is a Device Driver (DD)?
A Device Driver is a piece of code that manages some 
Users do not access a DD directly; Users make calls
to some OS-defined Application Programming 
Interface (API). The API will then end up calling 
the Device Driver.   This makes the user code 
independent of the Device Driver code.
The Hardware Vendor writes the device driver. The 
device driver must supply some set of function calls  
to be used by the OS.  This set of function calls
is known as the Device Driver Interface (DDI).