.. 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