The crc command is used to record the length and 16-bit CRC value (or, optionally, the 32-bit CRC value) for one or more files.
The crcchk command is used to record the length and CRC value (either 16-bit or 32-bit) for a list of files and optionally check their lengths and CRC values against a previously-obtained set of values for those files.
The code used to calculate the 16-bit CRC value for an individual file was developed at IBM Austin, Texas, by Jim Czenkusch. The code to calculate the 32-bit CRC has enhancements to pre-condition and post-condition each value so that it is compatible with the 32-bit CRC value generated by PKWARE's PKZIP and InfoZIP's zip commands.