There is probably a calculator builtin to your Operating System. For Windows, press startup (Bottom left) and then type calculator in the window ("Search programs and files"). Macs probably also have them.
Google also provides one. Just type "calculator" and woosh  you have one.
Google can also be used to plot functions. Just type sin(x)/x in the Google search window it's a cool function (sinc(x)) which has MANY applications in physics (RF). Virtually any function of x can be plotted. Just type the equation  ie: x^3 +12x^2 4x +1 and hit enter  wooosh!!!
Handheld calculators are already obsolete ;)
1/9/2014

Tom D.