CDCheck was created to eliminate or at least minimize bad copies, provide efficient error detection and offer recovery.

A short list of when and why you should use particular parts of CDCheck:

CRC
CRC is the ultimate tool for detecting file changes and therefore for detecting errors. Every storage device has some algorithms for error detection but you never now how good they are. So it is nice to have something extra ready to be sure your files are safe.

CRC should be used when:
- making backups: to be able to verify integrity of backup after some time (months, years)
- making important copies: to be able to verify integrity of copies after some time (months, years)
- moving data: to verify integrity before deleting the original files
- you want to be sure no one/nothing has changed your files
- you want to check integrity without having the original files
- preparing important data to be sent through less reliable media (internet, serial port...): so that on the other end you can verify integrity of data without having the original

Checking
Checking combines two things: CRC verification and checking accessibility/readability of files. It is the main diagnostic feature. Checking should only be used if compare cannot be done because compare is much safer!!

Checking should be used when:
- you suspect some files are not readable: to asses the damage of files
- you want to verify that all files/directories are readable: to be sure everything is fine
- you want to verify CRC
- when you change drivers for CDR, purchase a new CDR or use new cdr media: to make sure it functions correctly

Compare
Compare is used to verify that two directories contain the same files and have the same content. Accessibility/readability of files is checked at the same time (as when using Checking). This is the preferrable way of verifying file integrity if you have original files.

Compare should be used when:
- making backups: to be sure backup is done correctly (CRC creation is recomended)
- making important copies: to verify integrity of copies (CRC creation is recomended)
- moving data: to verify integrity before deleting the original files
- you suspect some files are not readable: to asses the damage of files
- you want to verify that all files/directories are readable and same as the original: to be sure everything was copied correctly
- you want to find out which files are missing in directories and/or are different: to get a list of differences - when you change drivers or firmware or CDR, change burning software, purchase a new CDR or use new cdr media brand: to make sure it functions correctly

Recovery
Recovery is used to try to recover damaged files. All unrecovered parts of files are filled with zeros.

Recover should be used when:
- read errors are detected by Checking or Compare: to recover data and save it elsewhere
- while copying a file you get "Cannot copy" or "Cannot read" etc.: to recover good part of data and save it elsewhere
- you suspect that file was copied incorrectly: to try to make copy without errors

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