C++ program to implement a digit class and make use of operator overloading:

Digitclass.cpp

    #include<iostream>
    using namespace std;
    class digit{
        int val;
        public:
            digit();
            digit(int num);
            friend istream& operator >>(istream& inp,digit &a){
                inp>>a.val;
                return inp;
            }
            friend ostream& operator <<(ostream& out,digit &a){
                out<<a.val;
                return out;
            }
            digit operator ++();    // for prefix usage
            digit operator ++(int);  // for postfix usage
            digit operator --();  // for prefix usage
            digit operator --(int); // for postfix usage
    };
    digit::digit(){
        val=0;
    }
    digit::digit(int num){
        val=val;
    }
    digit digit::operator++(){
        val++;
        if(val==10)val=0;
        digit t(val);
        return t;
    }
    digit digit::operator++(int){
        digit t(val);
        val++;
        if(val==10)val=0;
        return t;
    }
    digit digit::operator--(){
        val--;
        if(val==-1)val=9;
        digit t(val);
        return t;
    }
    digit digit::operator--(int){
        digit t(val);
        val--;
        if(val==-1)val=9;
        return t;
    }
    int main()
    {
        cout<<"Choice : 1)Pre increment 2) Post increment 3) Pre decrement 4) Post decrement 5) Exit";
        digit d;
        int ch;
        cout<<"\nEnter any digit..";
        cin>>d;
        while(1){
            cout<<"\nEnter your choice ";
            cin>>ch;
            if(ch==1){
                ++d;
                cout<<"The new value is "<<d;
            }
            else if(ch==2){
                d++;
                cout<<"The new value is "<<d;
            }
            else if(ch==3){
                --d;
                cout<<"The new value is "<<d;
            }
            else if(ch==4){
                d--;
                cout<<"The new value is "<<d;
            }
            else{
                break;
            }
        }
        return 0;
    }