Yacas (Yet Another Computer Algebra System) is a small and highly flexible general-purpose Computer Algebra System (CAS). The syntax uses an infix-operator grammar parser. The distribution contains a small library of mathematical functions, but its real strength is in the language in which you can easily write your own symbolic manipulation algorithms. The core engine supports arbitrary precision arithmetic and is able to execute symbolic manipulations on various mathematical objects by following user-defined rules. For detailed information on yacas features and usage, see http://www.yacas.org.