"why we are using C language for writing drivers and OS codes.?"
So that programmers won't have to learn new syntax of each new assembly language for each new kind of machine.
"Is there any drivers written in any other languages?"
Historically, assembly languages. I don't remember if PL/S or BLISS could be used for drivers. Maybe B. In modern times, a few brave people use C++ but they have to be very careful. C++ can be used a bit more easily in user mode drivers in some situations.
