But yes if people get hungry enough, field corn easily qualifies as actual food.
Sweet Corn: For Fresh Eating and therefore harvested with a high moisture content which hurts preservation without freezing and total yield.
Dimple is a Field corn, harvested later resulting in a dryer product, lasts longer and has a higher yield.
Flint Corn: Mostly decorative as it looks cool, but again still edible after grinding.
Heirloom: lots of shapes and sizes but significantly lower yield.
Popcorn: A tiny slice of the market but pops when heated.
Corn is amazing. My favorite use of it is for alcohol though.