A little calculator written in BCX basic and then translated to C code and modified to compile with Dev C++ (GCC/G++). Once you find your way past the standard GUI gibberish you can figure it out.
For those who need some hand holding with the Dev C++ IDE:
In the IDE go to FILE, then NEW, then Project, select Windows Application, give it a name like Calc1 then click OK. A filesave dialog box comes up, create a new folder, might as well call it Calc1, open it and save Calc1.dev there. The DevCpp IDE comes up with a bare bones template, select and delete that and cut and paste this code into the empty editor page. Now compile and run.