CS-100 In-Class Project: The Rainbow Calculator Full Operation

Instructions:

1. Download the form for this project from the website: Rainbow Calculator
2. Write a program completing the four function calculator. Working from the keypad you have already completed, add code for the command buttons: Add (+), Subtract (-), Multiply (X), Divide (/) and Equal (=)
3. Your calculator must be able to handle "running totals". After the equal key is pressed you can then perform another arithmetic operation using the result of the last one. For example: Suppose you want to add 5 plus 3 then multiply the result by 7. You press the "5" key, followed by the "+" key, followed by the "3" key, followed by the "=" key. This produces a sum of 8 in the picture box. Now you can press the "X" key followed by the "7" key followed by the "=" key to get the result 56 in the picture box. From here you can continue with any other sequence of operations.
4. As you have seen already, you create a number in the picture box by clicking the keys on the keypad.
5. Now you will add the code to perform the arithmetic operations. Here is the sequence of things that you must do:
   • Whenever any one of the arithemetic buttons (+, -, X, or /) is clicked.
     • convert the string held in global variable num_str to a numeric value and save it in global variable op_one
     • set a flag (global variable fun_code) to remember what operation was performed. (Let fun_code = 1 for addition, fun_code = 2 for subtraction etc.)
     • reset the variable num_str such that it contains no characters.
   • When the equal (=) button is pressed you will have two values on which to work. The first one is already converted to a number and stored in global variable op_one. The second value is still in string form and held in global variable num_str. To complete the calculation you must do the following:
     • check the global variable fun_code to determine what operation to perform (+, -, X, or /), then perform the operation saving the answer in a local variable such as result. The general form for the computation will be:
       Let result = op_one + Val(num_str) if the fun_code represents addition.
     • print the answer to the picture box
     • A critical final part will be to save the answer so that it can be used in successive calculations. To do this convert the result to a string and save it in variable num_str. e.g. Let num_str = str(result)