What are the functions of variable attenuator?
Neither the C nor C++ languages specify variable attenuators. In
engineering, an "attenuator" is something that reduces the
amplification of a signal or other source. The closest C or any
other programming language would come to such an operation is
through the negative "-", divide "/" or bitwise-right ">>"
operators.
If this is in reference to a library which interacts with a
physical mechanism through C, you will need to refer to the manual
for the library's API for further information.