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From: kevin@ttidca.TTI.COM (Kevin Carothers)
Newsgroups: alt.sources
Subject: mortgage interest calculator
Message-ID: <5292@ttidca.TTI.COM>
Date: 10 Aug 89 19:32:44 GMT
Organization: Citicorp/TTI, Santa Monica
Lines: 118

Hi -
I don't know if I posted this here before, but here it is anyway.
I am posting my loan-interest program that I originally posted in
"misc.consumers" a couple of years ago. Instructions are easy. 
Seems like a lot of people from Europe are picking up this newsgroup,
so I can't vouch for Overseas banking interest formulae. 
Any problems, let me know.
---------------------------------------------------------------------
 
/*
 * Program to print a mortgage payment
 * debt over a period of years
 */

#include <stdio.h>

main()
{
	int c,i;
	float mort_amt;
	float mort_int;
	float mort_pmt;
	float intrst;
	int  mort_yrs;
	float t_int;
	float t_t;
	float t_tmp;
	float temp;
	float tmp_amt;
	float tmp_int;
	int tmp_yrs;
	int  y_yrs;
	float y_int;
	float y_t;
	float y_tmp;
	
	printf("Enter the loan amount: ");
	scanf("%f",&mort_amt);

	printf("Enter the years of the loan: ");
	scanf("%d",&mort_yrs);
	tmp_yrs=mort_yrs;

	printf("Enter the interest rate: ");
	scanf("%f",&mort_int);

	if(mort_int < 1.) mort_int *= 100.;
	intrst = (mort_int/100.)/12.;
	mort_yrs *= 12;
	temp = 1.;

	do {
		temp *= (1. +intrst);
		mort_pmt += (1./temp);
		mort_yrs--;
	} while(mort_yrs > 0);

	temp = mort_amt/mort_pmt;
	mort_int /= 100.;
	y_tmp = y_int = y_t = 0.;
	mort_yrs = 0;
	tmp_amt = mort_amt;

		printf("\nloan amount: $%6.2f\t\t",tmp_amt);
		printf("loan rate: %4.2f%\n",mort_int*100.);
		printf("monthly payment: $%10.2f\n\n",temp);

		if((c=getchar()) != EOF)
		    if((c=getchar()) == EOF)
			exit();
			
	do {
	
		printf("year: %d",++mort_yrs);
		printf("\nloan amount: $%6.2f\t\t",tmp_amt);
		printf("loan rate: %4.2f%\n",mort_int*100.);
		printf("monthly payment: $%10.2f\n\n",temp);

		printf("month\tpayment\t\tinterest\tprincipal\tbalance\n");
		printf("-----\t-------\t\t--------\t---------\t-------\n");

		t_tmp = t_int = t_t = 0.;
		for(i=1 ; i <= 12 ; ++i) {

			if(mort_amt <= .01) {
				mort_yrs = tmp_yrs;	/* force exit   */;
				break;
			}
			tmp_int = temp - (mort_amt*(mort_int/12.));
			mort_amt -= tmp_int;

			printf("%2d\t$%7.2f\t$%7.2f\t$%7.2f\t$%7.2f\n",
				i,temp,temp-tmp_int,tmp_int,mort_amt);

			t_tmp += temp;
			t_t += tmp_int;
			t_int +=temp-tmp_int;
	
			y_tmp+= temp;
			y_t += tmp_int;
			y_int += temp-tmp_int;

		}

		printf("     \t_______\t\t________\t_________\n");
	    	printf("     \t$%7.2f\t$%7.2f\t$%7.2f\n",t_tmp,t_int,t_t);

		printf("     \t_______\t\t________\t_________\n");
	    	printf("     \t$%7.2f\t$%7.2f\t$%7.2f\n",
		  y_tmp,y_int,y_t);

		printf("     \t=======\t\t========\t=========\n");

		if((c=getchar()) == EOF)
			break;
				
	} while(mort_yrs< tmp_yrs);
}