//"Age.cpp". This program accepts from the system the current date and 
//     displays this date. Itinputs from the keyboard a user's 
//     date of birth, verifies  with the user if  these dates 
//     were accepted correctly, then calculates the exact age of 
//     the user in years, months and days and displays this age 
//     together with both dates. 
//Programmer: ...
//Date:       24.04.2002
//At:         ...

#include <iostream.h> //Responsible for the input/output commands
#include <conio.h>    //Responsible for the screen operations
#include <time.h>     //Handles Date and Time operations
#include <string.h>   //Handles string processing operations

void main()           //function 'main' heading
{                     //function'main' body

	//variables to hold digits extracted from the date
    int num1,num2,num3,num4,num5,num6;

    char answer = 'y';//variable to handle the answer
    int DD;			  //variable to handle the system current date
	int MM;           //variable to handle the system current month
	int YY;           //variable to handle the system current year
    int BIRTH_DD;     //variable to handle the day of birth
	int BIRTH_MM;     //variable to handle the month of birth
	int BIRTH_YY;     //variable to handle the year of birth
    int DIFF_DD;      //variable to handle the difference between
	                  //the current date and the dau of birth
	int DIFF_MM;      //variable to handle the difference between 
	                  //the current month and the month of birth
	int DIFF_YY;      //variable to handle the difference between 
	                  //current year and the year of birth  
    int USER_DD;      //variable to handle the date entered by 
	                  //the user
	int USER_MM;      //variable to handle the month entered by 
	                  //the user
	int USER_YY;      //variable to handle the year entered by 
	                  //the user
    int AGE_M;        //variable to handle age in months
	int AGE_D;        //variable to handle age in days

	char date[128]; //variable to hold the system date
	_strdate (date);//function that accepts the system date

	//Message explanation of the program content
	 cout<<"Dear user! You are wellcome to run this program!"<<endl;
	 cout<<endl;
     cout<<"This program accepts from the system the current"<<endl;
	 cout<<"date and displays this date. It inputs from the "<<endl;
	 cout<<"keyboard a user's date of birth, verifies  with "<<endl;
	 cout<<"the user if  these dates were accepted correctly, "<<endl;
     cout<<"then calculates the exact age of the user in years"<<endl;
	 cout<<"months and days and displays this age together "<<endl;
	 cout<<"with both dates. "<<endl<<endl;


    //message to display the system current date    
	cout<<"\nToday date is: ["<<date<<"]"<<endl;

	//This part of the code shifts the characters 
	//of date into separate 'char' variable
	num1=date[3];
	num2=date[4];
	DD=(num1-48)*10+(num2-48)*1;//conversion of 
	//characters into integer

	//displays the day
    cout<<"The day is:   "<<DD<<endl;

	num3=date[0];
	num4=date[1];
	MM=(num3-48)*10+(num4-48)*1;//conversion of 
	//characters into integer

	//displays the month
    cout<<"The month is: "<<MM<<endl;

	num5=date[6];
	num6=date[7];
	YY=((num5-48)*10+(num6-48)*1)+2000;//conversion of 
	//characters into integer

	//displays the year
    cout<<"The year is:  "<<YY<<endl<<endl;

	//until the answer is not equal 'n'
    while (answer != 'n')
    {
	//message prompt for the user
    cout<<"Would you like to see this program at work? (Y/N or y/n) "<<endl<<endl;
    cin>>answer; //accepts the answer from the keyboard
    cout<<endl;

	//if condition is equal 'y' or 'Y'
    if (answer == 'Y' || answer == 'y')
    {
		//message prompt for the user to enter a day of birth
        cout<<"Please enter a day of your birth (e.g. 25): "<<endl;
        cin>>BIRTH_DD;  //accepts the date

		//message prompt for the user to enter a month of birth
        cout<<"Please enter a month of your birth (e.g. 8): "<<endl;
        cin>>BIRTH_MM;  //accepts the month

		//message prompt for the user to enter a year of birth
        cout<<"Please enter a year of your birth (e.g. 2001): "<<endl;
        cin>>BIRTH_YY;  //accepts the year
        cout<<endl<<endl;

		//message to get user's confirmation for the date of birth
        cout<<"Is the date of your birth: "<<BIRTH_DD<<"/"<<BIRTH_MM<<"/"
             <<BIRTH_YY<<" ?"<<endl;

		//message to get user's confirmation for the current date
        cout<<"Is the current date: "<<DD<<"/"<<MM<<"/"<<YY<<" ? (y/n or Y/N)"
             <<endl<<endl;
        cin>>answer;   //accepts the answer
        cout<<endl;

		//if condition is equal 'n' or 'N'
        if (answer == 'n' || answer == 'N')
        {
			//message prompt for the user to enter a day of birth
            cout<<"Please enter a day of your birth (e.g. 27): "<<endl;
            cin>>BIRTH_DD; //accepts the birth Day

			//message prompt for the user to enter a month of birth
            cout<<"Please enter a month of your birth (e.g. 12): "<<endl;
            cin>>BIRTH_MM; //accepts the birth month

			//message prompt for the user to enter a year of birth
            cout<<"Please enter a year of your birth (e.g. 1997): "<<endl;
            cin>>BIRTH_YY; //accepts the birth year
			
            cout<<endl<<endl;
			//message prompt for the user to enter current date
            cout<<"Please enter the current day (e.g. 28): "<<endl;
            cin>>USER_DD; //accepts the user date

			//message prompt for the user to enter current month
            cout<<"Please enter the current month (e.g. 6): "<<endl;
            cin>>USER_MM; //accepts the user month

			//message prompt for the user to enter current year
            cout<<"Please enter the current year (e.g. 2002): "<<endl;
            cin>>USER_YY; //accepts the user year
            cout<<endl;

			//if the birth day less that user date and birth month is
			//less than user month
            if(BIRTH_DD<=USER_DD && BIRTH_MM<=USER_MM)
             {
				//calculation of different year, month, date
                DIFF_YY=USER_YY-BIRTH_YY;
                DIFF_MM=USER_MM-BIRTH_MM;
                DIFF_DD=USER_DD-BIRTH_DD;
             }
				//if the birth day greater that user date and birth 
			    //month is greater than user month
                if(BIRTH_DD>=USER_DD && BIRTH_MM>=USER_MM)
                {
					//calculation of different year, month, date
                    DIFF_YY=USER_YY-BIRTH_YY-1;
                    DIFF_MM=12-BIRTH_MM+USER_MM-1;
                    DIFF_DD=30-BIRTH_DD+USER_DD;
                }
					//if the birth day greater that user date 
				    //and birth month is less than user month
                    if (BIRTH_DD>USER_DD && BIRTH_MM<USER_MM)
                    {
						 //calculation of different year, month, date
                         DIFF_YY=USER_YY-BIRTH_YY;
                         DIFF_MM=USER_MM-BIRTH_MM-1;
                         DIFF_DD=30-BIRTH_DD+USER_DD;
                    }
						//if the birth day less that user date 
				        //and birth month is greater than user month
                        if (BIRTH_DD<USER_DD && BIRTH_MM>USER_MM)
                        {
							//calculation of different year, month, 
							//date
                            DIFF_YY=USER_YY-BIRTH_YY-1;
                            DIFF_MM=12-BIRTH_MM+USER_MM;
                            DIFF_DD=USER_DD-BIRTH_DD;
                        }
		//message to confirm that the date was entered correctly
        cout<<"The current date you entered is: "
			<<USER_DD<<"/"<<USER_MM<<"/"
            <<USER_YY<<endl;
        }
		
	    //if condition is equal 'y' or 'Y'
        if (answer == 'y' || answer == 'Y')
        {
	        //if the birth day is less that current date 
			//and birth month is less than current month
            if(BIRTH_DD<=DD && BIRTH_MM<=MM)
            {
				//calculation of different year, month, 
				//date
                DIFF_YY=YY-BIRTH_YY;
                DIFF_MM=MM-BIRTH_MM;
                DIFF_DD=DD-BIRTH_DD;
            }
				//if the birth day is greater that current date 
				//and birth month is greater than current month
                if(BIRTH_DD>=DD && BIRTH_MM>=MM)
                {
					//calculation of different year, month, 
					//date
                    DIFF_YY=YY-BIRTH_YY-1;
                    DIFF_MM=12-BIRTH_MM+MM-1;
                    DIFF_DD=30-BIRTH_DD+DD;
                }
					//if the birth day is greater that current date 
				    //and birth month is less than current month
                    if (BIRTH_DD>DD && BIRTH_MM<MM)
                    {
						 //calculation of different year, month, 
						 //date
                         DIFF_YY=YY-BIRTH_YY;
                         DIFF_MM=MM-BIRTH_MM-1;
                         DIFF_DD=30-BIRTH_DD+DD;
                    }
						//if the birth day is less that current date 
				        //and birth month is greater than current month
                        if (BIRTH_DD<DD && BIRTH_MM>MM)
                        {
							//calculation of different year, month, 
							//date
                            DIFF_YY=YY-BIRTH_YY-1;
                            DIFF_MM=12-BIRTH_MM+MM;
                            DIFF_DD=DD-BIRTH_DD;
                        }
        }

   //Message to display the date of birth
   cout<<"The date of your birth is: "<<BIRTH_DD<<"/"<<BIRTH_MM<<"/"
       <<BIRTH_YY<<endl;
   //Message to display system current day
   cout<<"The system current date is: "<<DD<<"/"<<MM<<"/"<<YY<<"."<<endl;
   //Message to display users age 
   cout<<"\nYour age is: "<<DIFF_YY<<" years "<<DIFF_MM<<" months "<<DIFF_DD
       <<" days "<<endl<<endl;
   //Message to display users age in years
   cout<<"Your age in years is: "<<DIFF_YY<<" years."<<endl;

   //calculates age in months
   AGE_M=DIFF_YY*12+DIFF_MM;
   //Message to display users age in months
   cout<<"Your age in months is: "<<AGE_M<<" months."<<endl;

   //calculates age in days
   AGE_D=DIFF_YY*365+DIFF_MM*30+DIFF_DD;
   //Message to display users age in days
   cout<<"Your age in days is: "<<AGE_D<<" days."<<endl<<endl;
   }
   }
   //message to confirm the end of the program run
   cout<<"Good Bye - press enter to continue!";
   getch(); //stops the screen from vanishing, waiting for the input
            //from the keyboard  
}