Mathomatic™ is a portable, command-line, educational CAS and calculator software, written entirely in the C programming language. It is Free and Open Source Software (FOSS), published under the GNU Lesser General Public License (LGPL version 2.1), and has been under continual development since 1986. The software can symbolically solve, simplify, combine, and compare algebraic equations, simultaneously performing generalized standard, complex number, modular, and polynomial arithmetic, as needed. It does some calculus and is very easy to compile/install, learn, and use. The Mathomatic software consists of both a text-mode symbolic math application, and a symbolic math library, each suitable for desktops, servers, and mobile and embedded computer devices. It compiles and runs under any operating system with a C compiler, including Linux, Unix, Mac OS X, and MS-Windows (using MinGW or CygWin; MinGW works better and is standalone). An operating system is not required for running the Symbolic Math Library, which is Mathomatic’s symbolic math engine, and there are no dependencies other than the standard C libraries. Other programming languages able to link to C libraries should should have no problem using Mathomatic’s symbolic math engine, as long as reentrancy is not required.