So you can't afford a fancy graphing calculator. Or even a simple addition/subtraction/multiplication/division calculator. But you do have a Mac running Tiger. How fortunate.
Caveman's Calc is a digital slide rule - a digital analog calculator if you will. Like the real thing, the interface couldn't be simpler: just slide the middle portion left or right, allowing you to multiply, divide, take square roots, logarithms, inverses, and a couple of other surprises.
Caveman's Calculator is provided free of charge for you to enjoy.