A computer model is generally a <em>simulation</em> of the real world. Certainly, a model of Earth's climate is a simulation.
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In some cases, the data of interest is the performance of the computer itself (as opposed to some system outside the computer). In those cases, the running of the computer under different scenarios might be considered an <em>experiment</em>.
Hi! you can find the square root of a number with out a cauclater is to see if you can get to a whole number by squaring smaller numbers or multiplying a smaller number by it self.