Stupid Interest Calculator.cbl

      ******************************************************************
      * 
      * Stupid Interest Calculator
      * ==========================
      * 
      * A sample COBOL app to demonstrate the programming language
      * and make me doubt that I’m living in the 21st century.
      * 
      ******************************************************************

       IDENTIFICATION DIVISION.
       PROGRAM-ID. STUPID-INTEREST-CALCULATOR.
       
       
       DATA DIVISION.
       
       
       FILE SECTION.
       
        
       WORKING-STORAGE SECTION.
      * In COBOL, you declare variables in the WORKING-STORAGE section.
       
      * Let’s declare a string variable for the user’s name.
      * The string will be 20 characters in size.
       77 USER-NAME            PIC A(20).
       
      * The standard input variables for comouting interest.
      * The principal will be a 6-digit whole number, while
      * the interest rate and years will be 2-digit whole numbers.
       77 PRINCIPAL            PIC 9(6).
       77 INTEREST-RATE        PIC 9(2).
       77 YEARS                PIC 9(2).
       
      * And finally, variables to hold the results. Both will be
      * 5-figure numbers with 2 decimal places.
       77 SIMPLE-INTEREST      PIC 9(5).99.
       77 COMPOUND-INTEREST    PIC 9(5).99.
       
       
       PROCEDURE DIVISION.
      * Actual code goes here! 
       
       MAIN-PROCEDURE.
           PERFORM GET-NAME
           PERFORM GET-LOAN-INFO
           PERFORM CALCULATE-INTEREST
           PERFORM SHOW-RESULTS
           GOBACK.
       
      * Get the user’s name, just to demonstrate getting a string
      * value via keyboard input and storing it in a variable.
       GET-NAME.
           DISPLAY "Welcome to Bank of Murica!"
           DISPLAY "What’s your name?"
           ACCEPT USER-NAME
           DISPLAY "Hello, " USER-NAME "!".
           
      * Get the necessary info to perform an interest calculation.
       GET-LOAN-INFO.
           DISPLAY "What is the principal of your loan?"
           ACCEPT PRINCIPAL
           DISPLAY "What is the interest rate (in %)"
           ACCEPT INTEREST-RATE
           DISPLAY "How many years will you need to pay off the loan?"
           ACCEPT YEARS.
           
      * Do what who-knows-how-many lines of COBOL have been
      * doing for decades, and for about 95% of all ATM transactions.
       CALCULATE-INTEREST.
           COMPUTE SIMPLE-INTEREST = PRINCIPAL +
             ((PRINCIPAL * YEARS * INTEREST-RATE) / 100) - 
             PRINCIPAL
           COMPUTE COMPOUND-INTEREST = PRINCIPAL * 
             (1 + (INTEREST-RATE / 100)) ** YEARS - 
             PRINCIPAL.
           
       SHOW-RESULTS.
           DISPLAY "Here’s what you’ll have to pay back."
           DISPLAY "With simple interest: " SIMPLE-INTEREST
           DISPLAY "With compund interest: " COMPOUND-INTEREST.
                       
      * Yes, this needs to be here, and the name of the program
      * must match the name specified in the PROGRAM-ID line
      * at the start of the program, or COBOL will throw a hissy fit.
       END PROGRAM STUPID-INTEREST-CALCULATOR.