fx-Calc is actually one of the most advanced desktop calculators for Windows. Starting with a simple calculator window, it allows already calculating self defined functions, sums and products. It takes for instance just a few clicks to run the Leibnitz iteration to calculate Pi. fx-Calc lets you define, analyse, visualise and calculate scientific functions and is a full featured replacement and/or enhancement of the old fashioned Windows calculator. Additional to calculation and visualization you can analyze and solve scientific functions and perform linear regression. Even if the Window concept may not look advanced, it provides the big advantage to open similar windows multiple times and compare the results as needed.