Imports System
Imports Microsoft.VisualBasic
Imports LoanLib

Public Class LoanApp
    
    Public Shared Sub Main()
        Dim Args As String()
        Args = System.Environment.GetCommandLineArgs()

        Dim ln As New Loan()
        
        If Args.Length < 5 Then
            Console.WriteLine("Usage: ConLoan Balance Rate Term Payment")
            Console.WriteLine(" Either Balance, Rate, Term, or Payment " _
                                & "must be 0")
            Exit Sub
        End If
        
        ln.OpeningBalance = Convert.ToDouble(Args(1))
        ln.Rate = Convert.ToDouble(Args(2)) / 100.0
        ln.Term = Convert.ToInt16(Args(3))
        ln.Payment = Convert.ToDouble(Args(4))
        
        If ln.OpeningBalance = 0.0 Then
            ln.ComputeOpeningBalance()
        End If
        If ln.Rate = 0.0 Then
            ln.ComputeRate()
        End If
        If ln.Term = 0 Then
            ln.ComputeTerm()
        End If
        If ln.Payment = 0.0 Then
            ln.ComputePayment()
        End If 
        Console.WriteLine("Balance = {0,10:0.00}", ln.OpeningBalance)
        Console.WriteLine("Rate    = {0,10:0.0%}", ln.Rate)
        Console.WriteLine("Term    = {0,10:0.00}", ln.Term)
        Console.WriteLine("Payment = {0,10:0.00}" & ControlChars.Cr, _
                          ln.Payment)
        
        Dim MorePmts As Boolean
        Dim Balance As Double = 0.0
        Dim Principal As Double = 0.0
        Dim Interest As Double = 0.0
        
        Console.WriteLine("{0,4}{1,10}{2,12}{3,10}{4,12}", _
           "Nbr", "Payment", "Principal", "Interest", "Balance")
        Console.WriteLine("{0,4}{1,10}{2,12}{3,10}{4,12}", _
           "---", "-------", "---------", "--------", "-------")
        
        MorePmts = ln.GetFirstPmtDistribution(ln.Payment, Balance, _
           Principal, Interest)
        
        Dim PmtNbr As Short
        
        While MorePmts

            Console.WriteLine("{0,4}{1,10:0.00}{2,12:0.00}{3,10:0.00}" _
              & "{4,12:0.00}", PmtNbr, ln.Payment, Principal, Interest,
              Balance)
            MorePmts = ln.GetNextPmtDistribution(ln.Payment, Balance, _
              Principal, Interest)
            PmtNbr += CShort(1)
        End While
    End Sub
End Class
[C#]
using System;
using LoanLib;

public class LoanApp {
   public static void Main(String[] Args) {

      Loan ln = new Loan();
      
      if (Args.Length < 4) 
      {
         Console.WriteLine("Usage: ConLoan Balance Rate Term Payment");
         Console.WriteLine("    Either Balance, Rate, Term, or Payment 
            must be 0");
         return;
      }

      ln.OpeningBalance = Convert.ToDouble(Args[0]);
      ln.Rate = Convert.ToDouble(Args[1])/100.0;
      ln.Term = Convert.ToInt16(Args[2]);
      ln.Payment = Convert.ToDouble(Args[3]);
      
      if (ln.OpeningBalance == 0.00) ln.ComputeOpeningBalance();
      if (ln.Rate == 0.00) ln.ComputeRate();
      if (ln.Term == 0) ln.ComputeTerm();
      if (ln.Payment == 0.00) ln.ComputePayment();

      Console.WriteLine("Balance = {0,10:0.00}", ln.OpeningBalance);
      Console.WriteLine("Rate    = {0,10:0.0%}", ln.Rate);
      Console.WriteLine("Term    = {0,10:0.00}", ln.Term);
      Console.WriteLine("Payment = {0,10:0.00}\n", ln.Payment);

      bool MorePmts;
      double Balance = 0.0;
      double Principal = 0.0;
      double Interest = 0.0;

      Console.WriteLine("{0,4}{1,10}{2,12}{3,10}{4,12}", "Nbr", "Payment",
        "Principal", "Interest", "Balance");
      Console.WriteLine("{0,4}{1,10}{2,12}{3,10}{4,12}", "---", "-------",
        "---------", "--------", "-------");

      MorePmts = ln.GetFirstPmtDistribution(ln.Payment, out Balance, 
        out Principal, out Interest);

      for (short PmtNbr = 1; MorePmts; PmtNbr++) {
         Console.WriteLine("{0,4}{1,10:0.00}{2,12:0.00}{3,10:0.00}
           {4,12:0.00}", PmtNbr, ln.Payment, Principal, Interest,
            Balance);
         MorePmts = ln.GetNextPmtDistribution(ln.Payment, ref Balance, 
           out Principal, out Interest); 
      }
    }
}

// Loan.cpp : Implementation of CLoan
#include "stdafx.h"
#include "math.h"
#include "LoanLib.h"
#include "Loan.h"

static double Round(double value, short digits); 

STDMETHODIMP CLoan::get_OpeningBalance(double *pVal)
{
    *pVal = OpeningBalance;
    return S_OK;
}

STDMETHODIMP CLoan::put_OpeningBalance(double newVal)
{
    OpeningBalance = newVal;
    return S_OK;
}

STDMETHODIMP CLoan::get_Rate(double *pVal)
{
    *pVal = Rate;
    return S_OK;
}

STDMETHODIMP CLoan::put_Rate(double newVal)
{
    Rate = newVal;
    return S_OK;
}

STDMETHODIMP CLoan::get_Payment(double *pVal)
{
    *pVal = Payment;
    return S_OK;
}

STDMETHODIMP CLoan::put_Payment(double newVal)
{
    Payment = newVal;
    return S_OK;
}

STDMETHODIMP CLoan::get_Term(short *pVal)
{
    *pVal = Term;
    return S_OK;
}

STDMETHODIMP CLoan::put_Term(short newVal)
{
    Term = newVal;
    return S_OK;
}

STDMETHODIMP CLoan::ComputePayment(double *pVal)
{
    Payment = Round(OpeningBalance * (Rate / 
        (1 - pow((1 + Rate), -Term))),2);
    *pVal = Payment;
    return S_OK;
}

STDMETHODIMP CLoan::ComputeOpeningBalance(double *pVal)
{
    OpeningBalance = Round(Payment / (Rate / 
        (1 - pow((1 + Rate), -Term))),2);
    *pVal = OpeningBalance ;
    return S_OK;
}

STDMETHODIMP CLoan::ComputeRate(double *pVal)
{
    double DesiredPayment = Payment;

    for (Rate = 0.001; Rate < 28.0; Rate += 0.001)
    {
        Payment = Round(OpeningBalance * (Rate / 
         (1 - pow((1 + Rate), -Term))),2);

        if (Payment >= DesiredPayment)
            break;
    }

    *pVal = Rate;   
    return S_OK;
}

STDMETHODIMP CLoan::ComputeTerm(short *pVal)
{
    double DesiredPayment = Payment;
    for (Term = 1; Term < 480 ; Term ++)
    {
        Payment = Round(OpeningBalance * (Rate / 
         (1 - pow((1 + Rate), -Term))),2);
        if (Payment <= DesiredPayment)
            break;
    }
    *pVal = Term;   
    return S_OK;
}

STDMETHODIMP CLoan::GetFirstPmtDistribution(double PmtAmt, double *Balance, double *PrinPortion, double *IntPortion, VARIANT_BOOL *pVal)
{
    *Balance = OpeningBalance;
    GetNextPmtDistribution(PmtAmt, Balance, PrinPortion, IntPortion, 
      pVal);
    return S_OK;
}

STDMETHODIMP CLoan::GetNextPmtDistribution(double PmtAmt, double *Balance, double *PrinPortion, double *IntPortion, VARIANT_BOOL *pVal)
{
    *IntPortion = Round(*Balance * Rate, 2);
    *PrinPortion = Round(PmtAmt - *IntPortion, 2);
    *Balance = Round(*Balance - *PrinPortion, 2);

    if (*Balance <= 0.0)
        *pVal = FALSE;
    else
        *pVal = TRUE;
    return S_OK;
}

STDMETHODIMP CLoan::get_RiskRating(BSTR *pVal)
{
    *pVal = (BSTR)RiskRating;
    return S_OK;
}

STDMETHODIMP CLoan::put_RiskRating(BSTR newVal)
{
    RiskRating = newVal;
    return S_OK;
}
static double Round(double value, short digits) 
{
    double factor = pow(10, digits);
    return floor(value * factor + 0.5)/factor;
}