From Alan's Stuff-Prudent Food Storage
http://athagan.members.atlantic.net/PFSFAQ/PFSFAQ-3-1.html#Grains
Corn Starch: A common starch used as a thickener. Made by a roller milling process removing the hull and germ leaving behind a nearly pure starch. Storage life is indefinite if kept dry. In the United Kingdom and some other areas it is known as corn flour which occasionally causes confusion with very finely milled corn also known as corn flour here in the States. The two products are largely not interchangeable.