Mortgage Calculator

I know this must be a easy question, but for some reason I can not find the answer. I have a C++ Mortgage Calculator program and I just need to add a function to it. I want the user to have the ability to add a text file with data in it. Thank you

Here is the code:


#include <iostream>  
#include <cmath>    
#include <stdlib.h>  
using namespace std;
int main()
{

  double p;    
  double i;      
  int j;        
  int NumberOfPayments;
  int MonthlyPymtCtr;
  double m;    
  double LoanBalance;
  double MonthlyIntPd;
  double MonthlyPrinPd;
  const char NL='\n';
  const char TAB='\t';
  char listmore;
  int dividelist=0;  

  char quit;        
 

  quit = 'C';  
  while (quit != 'Q' && quit != 'q')
  {

     
  // loan data
                cout << "\n Mortgage web program";
                  cout << "\n ______________________________ ";
   
     
      cout<<"\n\nEnter Mortgage Amount: $";
      cin      >> p;
      cout<<"\n\nEnter Mortgage term in Years: ";
      cin      >> j;
      cout<<"\n\nEnter the Interest Rate: ";
      cin      >> i;
     
     // monthly payment calc
 
      m = p * (i/1200)/(1-pow(1+(i/1200),-1*(j*12)));
     

      //output payment amount
      cout<<"\nYour Monthly Payment is $"<<m<<".\n"<<endl;



      //loan balance and interest paid calculation
     

      NumberOfPayments = j * 12;  
      dividelist = 0;
     
      for (MonthlyPymtCtr=1; MonthlyPymtCtr<=NumberOfPayments; ++MonthlyPymtCtr)

      {
             
              MonthlyIntPd = p * (i/1200);
              MonthlyPrinPd = m - MonthlyIntPd;
              LoanBalance = p - MonthlyPrinPd;
              if (LoanBalance < 0)
                  LoanBalance = 0;
              p = LoanBalance;  
           
                       
             if (dividelist == 0)
             {
                 //cout<<"Loan Balance and Interest Paid\n\n";
                 cout<<"Loan Balance"<<TAB<<"Interest Paid"<<NL;
                 cout<<"____________"<<TAB<<"_____________"<<NL<<NL;
             }
             cout<<LoanBalance<<TAB<<TAB<<MonthlyIntPd<<NL;
             ++dividelist;
             
              if (dividelist==12)
              {
                  cout<<"Enter 'C' to continue,"<<"'N' for new data,"
                            <<"'Q' to quit>";
                  cin>>listmore;
                  if ((listmore=='C')||(listmore=='c'))
                      dividelist=0;
                  else if ((listmore=='N')||(listmore=='n'))
                      break;
                  else if ((listmore=='Q')||(listmore=='q'))
                      return 0;
               }
     }
     
            do      
        {
         cout<<"Enter C to continue, Q to quit>";

         cin>>quit;      
         cout<<'\n';
         } while ((quit!='q')&&(quit!='Q')&&(quit!='c')&&(quit!='C'));
           
       
  }
 
  //cout<<"Payment!\n";
 
  return 0;
}