Create a very simple four function integer calculator with buttons for Add, Subtract, Multiply, and Divide, and with two text-type input fields. When the user enters two numbers and clicks one of the buttons, the answer is displayed where shown. 

Your program must use an alert to tell the user about any errors. The possible errors include:

One or both input fields are blank

One or both input fields < -9999 or greater than 9999

Divide by zero

Illegal character in either input field.

Only 0, 1 ,2 ,3 ,4 ,5 ,6 ,7 ,8 ,9, and - are allowed.

You must include instructions to the instructor on how to install the assignment. In a separate file named ReadMe.txt. Even though there are none in the example, you must include instructions to the user.