code

#include <iostream>
#include <exception>

class Processor
{
public:

    enum class register_name
    {
        AX,
        BX,
        CX
    };

    int ax;

    int bx;

    int cx;

    void ShowRegisters()
    {
        std::cout << "ax = " + ax << std::endl << "bx = " + bx << std::endl << "cx = " + cx << std::endl;
    }

    void add(int num, register_name reg)
    {
        switch (reg)
        {
        case register_name::AX:
            ax += num;
            break;
        case register_name::BX:
            bx += num;
            break;
        case register_name::CX:
            cx += num;
            break;
        default:
            break;
        }
    }

    Processor()
    {
        ax = 0;
        bx = 0;
        cx = 0;
    }
};

int main()
{
    Processor proc;

    proc.add(10, Processor::register_name::AX);

    proc.ShowRegisters();

    return 0;
}