.. folks about this great paper, written by W Kahan:

Mathemtics Written in Sand.

"ABSTRACT: Simplicity is a Virtue; yet we

continue to cram ever more complicated circuits

ever more densely into silicon chips, hoping all

the while that their internal complexity will

promote simplicity of use. This paper exhibits

how well that hope has been fulfilled by several

inexpensive devices widely used nowadays for

numerical computation. One of them is the

Hewlett-Packard hp-15C programmable shirtpocket calculator ..."

http://www.cs.berkeley.edu/~wkahan/MathSand.pdf