Answer Posted / sai kiran

How a vehicle needs a driver to make the vehicle run
properly, similarly for an embedded systems a device driver
will make it run or work according to the user events or
timer events or through some h/w interrupts.

Its a software abstraction layer which will sit just above
the h/w. So an application can be written using the device
driver API calls. So depending on the API call being called
from application, the device which has been programmed to
do a specific task will be performed.

I want software development lifecycle of windows XP software?

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