Editing Ladder logic (section)

===Complex logic===
Here is an example of what two rungs in a ladder logic program might look like. In real-world applications, there may be hundreds or thousands of rungs.

Typically, complex ladder logic is "read" left to right and top to bottom. As each of the lines (or rungs) are evaluated the output coil of a rung may feed into the next stage of the ladder as an input. In a complex system there will be many "rungs" on a ladder, which are numbered in order of evaluation:
{{ordered list
 | start = 1
 | 1= Realising the function: A/C = Switch [[logical AND|AND]] (HiTemp [[logical OR|OR]] Humid).
<pre>
    ----[ ]---------+----[ ]-----+----( )
      Switch        |   HiTemp   |    A/C
                    |            |
                    +----[ ]-----+
                        Humid
</pre>
 | 2= Realising the function: Cooling = A/C [[logical AND|AND]] ([[logical NOT|NOT]] Heat).
<pre>
    ----[ ]----[\]--------------------( )
        A/C    Heat                 Cooling
</pre>
}}

This represents a slightly more complex system for rung 2. After the first line has been evaluated, the output coil "A/C" is fed into rung 2, which is then evaluated and the output coil "Cooling" could be fed into an output device "Compressor" or into rung 3 on the ladder. This system allows very complex logic designs to be broken down and evaluated.