The creation of a patch file involves the comparison of two versions of the file. The original version, also called the reference file, is compared against a newer version of the same file. ActivePatch then analyzes the differences between the two files, and those differences are saved in the patch file.

The patch file contains the changed data, along with the instructions needed to update an original version of the file so that its contents are identical to the new version. Additional information, such as the access and modification times of the file and its attributes, are also stored in the patch file. This ensures that the patched file is identical to the file that was used to create the patch.