COBOL I
Interactive Programming

For this application, we will develop an interactive program for finding the monthly payment for a house mortgage.

You will have ACCEPT and DISPLAY statements for the following:

• price of the house (pic 9(6))

• down payment on the house (pic 9(6))

• number of years to be financed (pic 99)

• annual interest rate (pic V9999)

You will then calculate the monthly payment on the house and display that value (with an appropriate label).

The formula is: 

Note - this formula uses the exponentiation operation - illustrated by the caret ^
here - but uses the ** in COBOL - see pages 267-270.

Your processing will be similar to this:

   3000-PROCESSING.
	PERFORM 3100-GET-VALUES.
	PERFORM 3200-CALCULATION.
	PERFORM 3300-DISPLAY-VALUES.
	PERFORM 3400-CONTINUE-ON.

    3100-GET-VALUES.
	DISPLAY "PLEASE ENTER THE PRICE OF THE HOUSE".
	ACCEPT HOUSE-PRICE.
	DISPLAY " ".
	DISPLAY "PLEASE ENTER THE DOWN PAYMENT".
	ACCEPT DOWN-PAYMENT.
	DISPLAY " ".
	DISPLAY "PLEASE ENTER THE YEARS TO BE FINANCED".
	ACCEPT YEARS.
	DISPLAY " ".
	DISPLAY "PLEASE ENTER THE INTEREST RATE (MUST INCLUDE A DECIMAL POINT)".
	ACCEPT RATE.

    3200-CALCULATION.
	COMPUTE PRINCIPLE = HOUSE-PRICE - DOWN-PAYMENT.
	COMPUTE MRATE = RATE / 12.  <-- if you use MRATE - define it as PIC V99999999.
         (I'm thinking of MRATE as monthly rate - thus the division by 12)
	COMPUTE PAYMENT = (insert formula here)

    3300-DISPLAY-VALUES.
	(insert coding to display payment amount - see additional comments below . . )

    3400-CONTINUE-ON.
	DISPLAY "DO YOU WANT TO CONTINUE WITH ANOTHER VALUE (Y/N)?".
	ACCEPT GO-ON-INDICATOR.

In your main module you will have:

    PERFORM 3000-PROCESSING UNTIL GO-ON-INDICATOR = "N".

Try processing with these values:

house price: 120000

down payment: 20000

years to finance: 30

interest rate (must include decimal): .0875 

(the payment should be about $786.70)

house price: 85000

down payment: 10000

years to finance: 30

interest rate (must include decimal): .0925

====================

Additional comments:
You can insert a SCREEN SECTION in the DATA DIVISION - after the Working-Storage Section.
SCREEN SECTION.
01 BLANK-SCREEN.
     05 BLANK SCREEN.

Add the following when you want a new screen:
DISPLAY BLANK-SCREEN.

Define PAYMENT-OUT  PIC $$$,$$9.99.  in Working-Storage

Then:
  MOVE PAYMENT    TO PAYMENT-OUT
  DISPLAY PAYMENT-OUT.