Question

Write a loan amortization program in C++. Assume the loan is paid off in equal monthly installments. To compute the monthly payment you must know: 1.the initial loan value 2. # of months the loan is in effect 3. APR. You should prompt the user for each of these 3 things then compute the monthly payment. The following formula is useful: Payment = (factor * value * monthly_rate) / (factor - 1) where factor = (1 + monthly_rate) ^ number_of_months. Then set up the amortization table that will show for each month the starting balance, the interest paid, the payment amount and the new balance. Use comments in the program and use a function that compute_payment given 3 values of loan amount, APR, and loan length. Most variables in the program should be doubles. The output should have headers for each column, echo the input values, and must be aligned.

Answer 1

#include<iostream>
#include<cstdlib>
#include<cmath>
#include<iomanip>

using namespace std;

// emi formula
double compute_payment(double amount,double rate,int month){
   double factor=pow(1+rate/1200.0,month);
   return((factor*amount*(rate/1200.0))/(factor-1));
}

int main(){
   double loan,interestRate;
   int month;

   // enter user loan amount
   cout << "Loan Amount: ";
   cin >> loan;
  
   // enter interest rate
   while(true){
       cout << "Interest Rate (% per year): ";
       cin >> interestRate;
      
       if(interestRate>0)   {
           break;
       }
       // if interest rate -ve
       else{
           cout<<"Interest rate must be positive.\n";
       }
   }
  
   // enter number of months
   while(true){
       cout << "Number of months: ";
       cin >> month;
       if(month>0){
           break;
       }  
       // if months are -ve
       else{
           cout<<"Month must be positive.\n";
       }
   }

    double monthlyPaid=compute_payment(loan,interestRate,month);
   
    // display EMI
   cout<<"\nEMI amount is $"<<monthlyPaid;
  
   cout << "\n\n*****************************************************************\n"
<< "\t\t\tAmortization Table\n"
<< "*****************************************************************\n"
<< "Month\tBalance\t\tPayment\t\tRate\tInterest\tPrincipal\n";
  
   // intially current month is 0
   int currentMonth=0;
   double interestTotal=0;
  
  
   while (loan > 0.01) {
      
       if (currentMonth == 0) {
           cout << currentMonth++ << "\t$"<<left<<fixed<<setw(12)<<setprecision(2)<< loan;
           cout << "\n";
       }
      
       else {      
           cout<<currentMonth++ <<"\t$";
           // calculate interest amount
           double interestAmt=loan*(interestRate/1200.0);
           // add interest
           interestTotal+=interestAmt;
           // sunbtract principal from loan amount
           loan-=(monthlyPaid-interestAmt);
           cout<<left<<fixed<<setw(15)<<setprecision(2)<<loan;      
          
           // display monthly payment
           cout<<"$";
           cout<<left<<fixed<<setw(15)<<setprecision(2)<<monthlyPaid;
           // disaply interest rate
           cout<<left<<fixed<<setw(12)<<setprecision(2)<<interestRate<<"$";
           // display interest amount
           cout<<left<<fixed<<setw(12)<<setprecision(2)<<interestAmt<<"$";
           // display principal
           cout<<left<<fixed<<setw(12)<<setprecision(2)<<(monthlyPaid-interestAmt)<<"\n";
      
       }
   }
  
   system("pause");
  
   return 0;
}