What kind of work can be done with c++ ?

Answer 1

C++ is a Turing-complete programming language. Ergo, you can do with C++ all that can be done with computers.

Answer 2

From a complex video game to a simple calculator.

Answer 3

Almost

Answer 4

... which is almost all you can probably imagine. As proven by theoretical computer science, there are limits for the computational model *all* current computers have and also it's unclear, if some of the artificial intelligence stuff we can imagine will ever be reachable but a lot, a lot is possible.