Project Barn Q3, width and depth of footings

hi!
I am planning a Pole Barn, part of which will be with a heated concrete floor. I will be asking questions to get the consensus expertise. Please stick to the topic, I will be asking several, and could easily miss your pearl of wisdom if you start crossing threads!
thanks!
Project Barn Q3, width and depth of footings
I am in North Texas, i doubt that the freeze line was ever more than 6 inches. Inside the Barn, about 1/2 of the floor space will be unheated compressed gravel, and 1/2 with the heated slab (separated by walls, of course).
Should i put footings on the outside perimeter (where the poles will be)?
If I do not put in a footing, how do I handle the gap between the exterior siding and the dirt?

I might be wrong here, but you really don't need footers if its not a load bearing wall.

If you are sinking poles into the ground... why not just put your poles in, wrap the bottom with a pressure treated ban board and then pure your floor, leaving the ban board there so you will be able to secure your siding to at the bottom or move it up a few inches to expose the cement. Now you will not have any gap between the slab and the siding.