Union Flag, Confederates...geez it sounds like the US around 1860.
While I am here I may as well offer some insight even though it may be disambiguous.
The "primary" difference between the style or type of plcs is mainly the number of I/O it can handle. Naturally the more I/O the more memory and features that are or may be available.
Some of the standard practice items for a plc have been things like traffic lights and a washing machine, either of which could probably work on a micro (small) plc because they do not need many I/O.
Another application that is used is a bottle filling line, where there may be more than one bottle filled at a time plus the conveyor(s) have to index...ie move X number of bottles into place then fill, refill filler and move X number of bottles into place. Naturally this would require more I/O and possibly some faster processing capabilities.
Now we get to a LARGE system. Think about an assembly line that makes different parts then assembles the parts to make an item then the item may be boxed, labeled, and stacked on pallets. As an example I worked with a fireproofing product that had material fed into a screw conveyor that fed a bucket elevator that put into a hopper, then went into a blender, after blending it dropped into 2 bagging hoppers, it used beam scales to weigh the bags as they filled, it also had a magazine rack that automatically fed bags to be placed on the spouts, the filled backs were kicked onto a conveyor that inclined, then had a positioning conveyor to turn the bags, placed in front of pusher then pushed over pallet, door opened and dropped bags onto pallet, pallet full it lowers then exits (new pallet goes into elevator), filled pallet goes to wrapper, after wrapped it goes to end where forklift takes away. Technically there was more to it then this brief description...but maybe you get the idea.
