============== There are four main sections of the U.S. statute governing patentability, and you only ever read about the first and third:

101: Patentable subject matter (what you can patent)

102: Anticipation (someone else invented or described it)

103: Obviousness (two or more references, taken together, describe it)

112: Specification (here’s the statute)

Most of what you read is about 101: is software a “thing” or is it a “mathematical formula” and thus not patentable?