All calculators looks the same to the user, what's special about this one is how easy it is to implement new functions for the programmer! Just use the function "GetNumber()" to get the next available number on the stack and you're ready to implement complex math function. I.e addition is simply done by using "GetNumber() + GetNumber()". What could be simpler? And we all know simple code means less bug fixing and a easier job for the maintainer... Hangs his head in same, Henrik