Equator is software designed to generate numerical values of over 200 mathematical functions in common use by engineers, scientists and others. Among the functions made available are simple ones such as cosines and binomial coefficients, as well as more complex examples such as Bessel functions and elliptic integrals. The Windows-based Equator software is available as an integral part of the book An Atlas of Functions, Second Edition, although its utility is not limited to users of this book. The Atlas is available in both print and electronic formats; full details can be found at www.springer.com. Equator is sold as a stand-alone unit, in part to benefit those who may access the electronic version of the Atlas through their library.