// Clock program using reference variables

#include <iostream>
#include <iomanip>
using namespace std;

// Function prototypes
void delay1Second();
void advanceClock(unsigned short& hr, unsigned short& min, unsigned short& sec);

int main()
{
    unsigned short hours, minutes, seconds, duration;

    cout << "How many seconds do you want to run your clock? ";
    cin >> duration;

    cout << "Enter hours minutes seconds => ";
    cin >> hours >> minutes >> seconds;

    for (int i = 0; i < duration; i++)
    {
        delay1Second();
        advanceClock(hours, minutes, seconds);

        cout << setfill('0');
        cout << '\r' << setw(2) << hours << ':' << setw(2) << minutes << ':' << setw(2) << seconds << flush;
    }
}

void delay1Second()
{
    for (int i = 0; i < 400000000; i++) ;
}

void advanceClock(unsigned short& hr, unsigned short& min, unsigned short& sec)
{
    ++sec;
    min += sec/60;
    hr += min/60;
    sec %= 60;
    min %= 60;
    hr %= 24;
}