C++ code showing Inheritance and Data Conversion

This is the solution for T.U. 2067 Q.N.3

#include <iostream>

using namespace std;

class clock
{
protected:
    int hr, min, sec ;
public:
    clock()
    {
        hr = min = sec = 0;
    }
    clock(int x)
    {
        hr = min = sec = x ;
    }
    void Show();
};

class wall_clock:public clock
{
    int TotalTime;
public:
    wall_clock():clock()
    {
        TotalTime = 0 ;
    }
    wall_clock(int x):clock(x)
    {

    }
    void Add(int, int, int);
    void ShowTime();
};

void clock::Show()
{
    cout << endl << "Initially" << endl ;
    cout << endl << hr << ":" << min << ":" << sec << endl ;
}

void wall_clock::Add(int a, int b, int c)
{
    hr+=a;
    min+=b;
    sec+=c;
}

void wall_clock::ShowTime()
{
    if(sec>60)
    {
        min += sec/60;
        sec = sec%60;
    }
    if(min>60)
    {
        hr += min/60 ;
        min = min%60;
    }
    cout << endl << hr << ":" << min << ":" << sec << endl ;
}

int main()
{
    wall_clock WC1,WC2;
    WC1 = 0 ;
    WC2 = 0 ;
    WC1.Show();
    WC2.Show();
    WC1.Add(1,17,65);
    WC2.Add(4,45,49);
    WC1.ShowTime();
    WC2.ShowTime();
    return 0;
}