FORSIM VI: a program package for the automated solution of arbitrarily defined differential equations. Nature of problem: Mathematical models comprising partial and ordinary differential equations arise in many scientific disciplines. A large class of these models may be automatically transformed into initial value problems involving only coupled ordinary differential equations, which may then be solved numerically by error-controlled integration. The FORSIM package solves a set of user-defined equations in this manner. These may be ordinary differential equations, and/or partial differential equations in up to three dimensions