# Exercise: Write code for a basic calculator using variables

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The answer to the exercise will be included and explained if you attend one of more of the courses listed below!

 Category ==> Visual C Sharp 2010  (65 exercises) Topic ==> C# variables  (4 exercises) Level ==> Average difficulty Courses ==> Introduction to Visual C#  /  WinForms using Visual C#
Before you can do this exercise, you'll need to download and unzip this file (if you have any problems doing this, click here for help).

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Press CTRL + D to add the file called frmCalculator.cs from the above folder into your project (or right click on the project and choose to add it as an existing item).

Change your project's properties to make this the default form for your project.  When you run your project, you should see a (very) basic calculator, which doesn't yet work.

Double-click on the Calculate button to create an event-handler for it.  In this event-handler, firstly use a Try ... Catch clause to check that you can read the two numbers entered into integer variables:

If a user has typed non-integer values into either of the boxes, as here, you should display an error message like the one shown and exit out of the subroutine.

If both of the numbers have been entered correctly, display the result in your event-handler:

Here clicking on the Calculate button should update the answer to 741,being the sum of 317 and 424.

That's it!  Now you just need to add multiplication, division, subtraction, sines, cosines, hyperbolic sines, square roots ...