[possiblywrong]

There was some amount of "standardization" of checksum methods to help with debugging typos. For example, Nibble magazine used a couple of programs-- the one I remember using was Key Perfect-- that would scan your program in memory after you typed it in, and report a series of short hex checksums, one for each reasonably small chunk of program (bytes for machine language, or lines of BASIC code). The magazine article would include the correct Key Perfect checksums for the program; compare against the generated report, and a difference meant you "only" had to scan a dozen lines of source instead of hundreds.