====== Input and output pins ======
[[plugins:calc:zeograph:userguide:filters|Filters]] send and receive data through pins. These pins come in two flavours:
  - //Input pins//, where filters receive input data before the filter is rendered, and;
  - //Ouput pins//, where filters push output data after the filter has been rendered.
Input pins are displayed on the left-hand side of a filter, and output pins are displayed on the right-hand side of a filter, as shown below:
|{{ :plugins:calc:zeograph:userguide:pins:filterexample.png |:plugins:calc:zeograph:userguide:pins:filterexample.png}} |
^  A filter with four input pins (left)
and one output pin (right).  ^
Input and output pins behave differently in some ways, as described below:
===== Input pins =====
  * You can manually edit the value of an input pin //if// it is not connected to another pin. 
===== Output pins =====
  * You cannot manually edit the value of an output pin. The value of an output pin is always and exclusively set by its parent filter.