Most editors have a feature like when you press some keys by placing caret over a function, it pops the documentation of that function along with number and type of arguments that function takes.I was wondering whether Vim offers such support. For example, while coding in C, I use a built in function qsort(). Since I am not sure about type and number of arguments it takes, I would like to know it without escaping Vim. Is it possible? 
How can I get Vim to show documentation of a C/C++ function?
autocompletion