A char is an integral type. When you write
char ch = 'A';
you're setting the value of ch to whatever number your compiler uses to represent the character 'A'. That's usually the ASCII code for 'A' these days, but that's not required. You're almost certainly using a system that uses ASCII.
Like any numeric type, you can initialize it with an ordinary number:
char ch = 13;
If you want do do arithmetic on a char value, just do it: ch = ch + 1; etc.
However, in order to display the value you have to get around the assumption in the iostreams library that you want to display char values as characters rather than numbers. There are a couple of ways to do that.
std::cout << +ch << '\n';
std::cout << int(ch) << '\n'