FreeCalc

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The calculator which comes with the Windows operating system is fine, but has limited functionality. FreeCalc has two useful features: you can copy/save/print the calculation, and even more usefully, it keeps a visual record of all the numbers you have entered, very useful if you are adding up a series of numbers and can't remember how far you have got.

Available from http://www.moffsoft.com/freecalc.htm