A source file xxx.f containing the Fortran subroutines FUNC, STPNT, BCND, ICND, FOPT, and PVLS. Here xxx stands for a user-selected name. If any of these subroutines is irrelevant to the problem then its body need not be completed. Examples are in auto/97/demos, where, e.g., the file ab/ab.f defines a two-dimensional dynamical system, and the file exp/exp.f defines a boundary value problem. The simplest way to create a new equations-file is to copy an appropriate demo file. For a fully documented equations-file see auto/97/gui/aut.f. In GUI mode, this file can be directly loaded with the GUI-button Equations/New; see Section 5.2.