# CellType Plugin¶

An example of the plugin that stores user assigned data that is used to configure simulation before it is run is a CellType Plugin. This plugin is responsible for defining cell types and storing cell type information. It is a basic plugin used by virtually every CompuCell simulation. The syntax is straight forward as can be seen in the example below:

<Plugin Name="CellType">
<CellType TypeName="Medium" TypeId="0"/>
<CellType TypeName="Fluid" TypeId="1"/>
<CellType TypeName="Wall" TypeId="2" Freeze=""/>
</Plugin>


Here we have defined three cell types that will be present in the simulation: Medium, Fluid, Wall. Notice that we assign a number – TypeId – to every cell type. It is strongly recommended that TypeId’s are consecutive positive integers (e.g. 0,1,2,3...). Medium is traditionally given TypeId=0 and we recommend that you keep this convention.

Note

Important: Every CC3D simulation must define CellType Plugin and include at least Medium specification.

Notice that in the example above cell type Wall has extra attribute Freeze="". This attribute tells CompuCell that cells of frozen type will not be altered by pixel copies. Freezing certain cell types is a very useful technique in constructing different geometries for simulations or for restricting ways in which cells can move.