Is it possible to write in C++ with C inserts?

Question

C++ / C#

while not doing too complicated manipulations

Answer 1

Well yes, use extern :

extern "C" {
        //сишный код
        int g(double);
        double h();
        ....
    };

Answer 2

So a generation of programmers was born for whom C and C++ are different languages. Dinosaurs see ++ as an addition to old C, in which the most useful thing is commenting with slashes //.
Seriously though, ask a question. All C ++ compilers compile pure C with a bang.
If you write cout in one line, and printf in the next line, the sky will not fall and the compiler will not scold, but it is unlikely that your question is so obvious, most likely something more complicated is meant .