In this chapter, propagation of round-off errors in floating
point arithmetic operations of computers numbers is presented.
The notions of the conditional number, stability
and complexity of algorithms are introduced and illustrated
by examples. The Horners scheme for evaluation of Polynomials
is given to elucidate the optimal and well-conditioned
algorithms when they are implemented in a computer system
like Mathematica. The chapter ends with a set of questions.
Keywords: Computer numbers, Round-off errors.