Checking files
To start checking you must first select the volume/directories/files which you wish to check. Checking is by default done with all subdirectories.

After that press "Check" button to show the Check setup confimation. In the setup you can change the source directory and CRC options.

You have two ways of checking files against CRC file created by CRC process. One is automatic detection that automatically searches and uses all CRC files found in directory and any subdirectory where checking is performed.

The other is custom CRC specification. Here you can specify your own CRC file agains which to check files. In this case all other CRC files found are ignored. If CRC file with same name as the one recommended during creation of CRC is found in "default CRC directory" default custom CRC filename is set to it.

Readability is tested always. If CRC is present or not.

Note! CRC file is always created relative to the selected source directory. Therefore when checking using custom CRC file you should always select the source directory for which CRC file was created. See also CRC creation for more information.

Tip: if you do not need the setup confimation dialog you can hold shift down while clicking the button and the checking will start with last options used and selected directory as source directory.

How reliable is checking without CRC files?
Checking is less reliable then compare and CRC checking but still very good. Checking ensures that files can be read from beginning to end and bytes read equal file size. This usually means that files are read correctly during this process. Because most of devices (cdrom, hard disk...) already have built in some low-level error detection they would otherwise during reding report any errors encountered. However different manufacturers have different policies what to do in cases when errors are encountered. Some try to correct it and if data is more or less corrected no error is returned. Others return error as soon as there is the slightest chance that there is an error.

How reliable is checking with CRC files?
If CRC files are present then checking is much more reliable. Then not only readability is tested but also the content itself. So if there is any file that was not read correctly or was changed the CRC algorithm detects that and CDCheck reports it. See also CRC creation for more information.

ADVANCED: Checking implementation
Checking is implemented using concurrent reading and CRC calculation. This is done by writing data from media into intermediate buffer in one thread and reading from buffer and calculating CRC values in other thread. CRCs are calculated whenever a CRC is detected of custom CRC is provided. Otherwise only reading is done. CRC values from CRC files are read sequentially as checking is progressing on a need basis in order to minimize memory usage.

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Copyright (C) 2002, Mitja Perko (CDCheck homepage)