//DISPLAY 12.1 Interface File for DigitalTime
//Header file dtime.h: This is the INTERFACE for the class DigitalTime.
//Values of this type are times of day. The values are input and output in
//24-hour notation, as in 9:30 for 9:30 AM and 14:45 for 2:45 PM.
#include <iostream>
using namespace std;

class DigitalTime
{
public:
    friend bool operator ==(const DigitalTime& time1, const DigitalTime& time2);
    //Returns true if time1 and time2 represent the same time;
    //otherwise, returns false.

    DigitalTime(int theHour, int theMinute);
    //Precondition: 0 <= theHour <= 23 and 0 <= theMinute <= 59.
    //Initializes the time value to theHour and theMinute.

    DigitalTime( );
    //Initializes the time value to 0:00 (which is midnight).

    void advance(int minutesAdded);
    //Precondition: The object has a time value.
    //Postcondition: The time has been changed to minutesAdded minutes later.

    void advance(int hoursAdded, int minutesAdded);
    //Precondition: The object has a time value.
    //Postcondition: The time value has been advanced
    //hoursAdded hours plus minutesAdded minutes.

    friend istream& operator >>(istream& ins, DigitalTime& theObject);
    //Overloads the >> operator for input values of type DigitalTime.
    //Precondition: If ins is a file input stream, then ins has already been
    //connected to a file.

    friend ostream& operator <<(ostream& outs, const DigitalTime& theObject);
    //Overloads the << operator for output values of type DigitalTime.
    //Precondition: If outs is a file output stream, then outs has already been
    //connected to a file.
private:
    int hour;
    int minute;
};