The geometry data sets for any model must be entered before any other data set. The model geometry is defined by two data sets; the nodal co-ordinate data set, and the element topology data set.

Nodal co-ordinates are entered using the routine DICOR. Information is entered one node at a time in ascending node order for all the nodes in the model. Only nodes referenced by elements in the element topology data set should be entered. No errors will occur if other nodes are entered. These additional nodes will, however, affect the scaling in the EYE FRAME command in FEMVIEW unless an element set has been defined.

Element topology is entered using routine DITOP. This routine is called once for each element in the model. The order of the nodal definition for an element has to be as defined in the Appendices to the FEMGV User Manual; any nodal re-ordering has to be performed for an element before calling routine DITOP. A second version of DITOP exists called DITOP2. This variant has an additional parameter IELVAR which is used to indicate particular analysis variants of a basic element geometry (see FEMGEN element variants). This value is set to zero by DITOP.

The nodal co-ordinates and element topology data sets may be entered in any order i.e. nodal co-ordinates then element topology, or element topology then nodal co-ordinates.