Type casting and converting numbers to strings are unrelated. Check out this site for what you are looking for:
These work for C and C++, but in C++ you need to #include cstdlib instead of stdlib.h. Also, some C++ compilers put some/all/none of these functions in namespace std, so watch out for that.
As far as casting, in C all you need to do is put the type to be casted to in parens:
int Num = (int) 'a';
That is frowned upon in C++, however. Take a look here for casting in C++:
The C-cast is equivalent to reinterpret_cast when used in C++, and can be dangerous when dealing with classes. It does serve useful for turning objects into raw data however (unsigned char).