Sqrt: this finds the square root of a number by Heron formula, although
the method was known to the Babylonians centuries before Hero

For techo speakers this is a convergent iterative method a value
(seed) often an initial guess is used to give an approximation.
The appoximation is used to generate another and so on giving
a sequence of improving approximate solutions for the problems.

The question then is, when does the program stop?.