Before the widespread availability of computers and powerful hand calculators, scientists usually sought exact (so-called analytic) functions to evaluate when solving equations. With computers, however, different strategies are possible. One such strategy is called the iterative strategy. A guess is made for the value used in a function, and the value of the function is calculated using that guess. Based upon the outcome, the guess is modified in an attempt to change the value of the function. The process is repeated over and over until the function comes within an acceptable range.

About iteration.