adpatch compares file versions before copying

What c-driver will do?

C-drive copies the files from patch unzipped directory to required location in u r application file system. Before copying it will check the file version of the existing file at the file system with the file version of the file in the patch. If the patch file version is higher than what it is at file system level then only c-driver will copy that files.

How adpatch will know the file versions of the patch delivered files?

With each patch a file with name f.ldt is delivered , which contain the file versions of the files delivered with the patch.
Adpatch will use this file to compare the file versions of files its delivering with the file on file system.