After starting the download, the program compares the data of files already stored in the download folder with the data stored in the download list and the data accessed by the server containing the file. If some difference is found during the comparison or the given file is not yet in the download folder, the program downloads the file. As a result, at the time of the download, the latest version of each file will be present.
The program stores the different file versions with the same name in an “old” folder. After downloading the files, the program creates a checksum which can be used to verify the integrity of the file set anytime. This is very important, eg when copying files.