CalcWrapper is a proof of concept and a clever solution for a simple problem: making the 4 basic operations. The way it works is ôeasyö. First, it launches Calculator (calc.exe) and then simulates typing using SendMessage. Finally, it retrieves the result value and displays it after closing Calculator. You see, CalcWrapper is a wrapper that combines the power of the too-much-complicated Ms Calculator and an easy-to-use Win32-based GUI.