Classic Computer Magazine Archive ANTIC VOL. 5, NO. 7 / NOVEMBER 1986

Calculate Your Car Loan

Payments you can live with


With Car Financer, you not only can figure out how much your monthly payments on a car (or any financed purchase) will be, but you can also determine how you might save money with different payment plans. This BASIC program works on all 8-bit Atari computers of any memory size, with disk or cassette.

This summer I was hit hard by "New Car Fever." I felt I must buy one or die trying, so I started looking for the automobile of my dreams. Then when I found it, I almost died of sticker shock.

I told myself to forget it, because there was nothing wrong with my current auto. However, for some reason the urge just wouldn't go away. And before I knew It I was sitting in front of my Atari trying to determine how much money I would need to scrape together for a down payment. This program is the result. Naturally it will also work with any other financed purchase, such as major appliances or vacation packages.

You can change any of the numbers to see how it alters the monthly payment. For instance, I found that if I added $200 to the down payment, I could pay off my loan in 30 months instead of 36.

Also, be warned that If you pay a sales tax rate different from the rate where you live, you'll probably get a bill from the state for the difference.


Type in Listing 1, CARFINAN.BAS, check It with TYPO II and SAVE a copy before you RUN it. When you start using the program, simply respond to the onscreen prompts.

In lines 30-350 the program asks you to input the price of the car you want, whether or not you'll be trading in another car, the tax rate, the down payment, miscellaneous expenses including tag and title, the finance rate, the number of months over which payment will take place, and the source of the loan (bank or car company).

Lines 360-380 determine your monthly payments if you borrow from a bank. This section is the formula Interest = Principal * Rate * Time.

Lines 390-470 calculate the payment If you go through the car company, which is better for you- especially if you pay off early, because you get back a refund of the interest. However, the routine for figuring out the monthly payment is more difficult. I Included a loop which takes place "M" times (with M being the number of months of the loan). The amount of monthly payment is adjusted until it falls to within $40 above or below the total amount financed. This should make little difference in the amount per payment, but that difference will vary according to the length of the loan. The amount won't be exact, but will give you a reasonable estimate.

Lines 480-1040 print the information either on screen or on a printer, and lines 1050-1070 and 2000-2010 are the option to quit or keep going. The [BREAK] key is disabled in lines 3000-3010.


Let's run through the program once as a demonstration. In my case, I bought a late-model Ford Bronco priced at $10,900 so we'll enter that number when prompted. For "Will you trade in?" we'll press [Y] for yes, and enter $3,400. We'll enter the sales tax rate at 4 percent, a down payment of $3,000, miscellaneous expenses (tag, title, etc.) at $5 and the finance rate at 15.25 percent. The loan will be paid over 30 months. Finally, when the program asks, "Will this loan be from 1. Bank, or 2. Car finance company (GMAC, Ford, etc.)," we'll press [2]-we're lucky enough not to have to go through secondary financing.

The screen shows the word "Working" in inverse video, which flashes as the program goes through the loop in lines 390-470. This might take a couple of minutes.

When the calculations are finished, we'll see the prompt, "Do you want the results on: 1. Screen, or 2. Printer?" We'll press [1] and the display should look like this:

When I found my
dream car, I
almost died of
sticker shock.

Price: $10900

Trade-in value: $3400

Tax rate: 4%

Down payment: $3000

Finance rate: 15.25%

Amount financed: $4805

Months: 30

Interest: 976.9

Total to repay: $5781.9

Monthly payment: $192.73

These figures don't take into account every minor expense, such as supplementary life insurance. But you'll get a very close estimate of your actual payments. Car Financer's estimate was within $3 of the actual monthly payment.

Car Financer helped me a lot, and I think it can help you, too. It puts your mind at rest by showing how much money a potential purchase will really cost you.

Elaine Patterson is a mathematics teacher from Blue Ridge, Georgia. This is her first publication in Antic.

Listing 1: CARFINAN.BAS Download