# Structure of the PRE File

The order of the cards in the .pre file specifies the order of the steps during the simulation.

There are two main types of cards in EDITFEKO:
Geometry cards
Cards used to create geometry and affect the meshing. These cards are used above the EG card.
Control cards
Cards used to define sources, loads, request and control the simulation. These cards are genearlly below the EG card, but can usually be used above the EG card as well.
The structure of the .pre file consists of the following sections:
1. Specify the mesh parameters.
1. Define the IP card. All cards following the IP card inherit the mesh settings set with this card.
2. Create the geometry.
1. Use the geometry cards to define the geometry of the model.
2. End with the EG card to indicate that the geometry creation is complete.
3. Specify the excitations, loads, frequency and output requests.
1. Use the control cards to define excitations, specify the frequency and add output requests.
2. End with the EN card to indicate the end of the file.

For control cards that define solution requests, “**” is used often as a label for that card. The label of a card is used by OPTFEKO to identify specific results. The label is also used by POSTFEKO for the identification of the solutions and output requests when post-processing simulation results.

For example:
**   Comments at the start the input file
...  Cards that define the geometry ** Comments
EG   End of the geometry
...  Control cards that define sources, special solution options
and indicate which quantities to calculate ** Card labels / comments
EG   End of the input file
Note:

All input and output parameters are in SI units (for example, lengths are in metres, potential in volts). All angles are in degrees.

See the SF, TG and IN cards to enter dimensions in different units and scale to metres.