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CRC32 Static Library for Microsoft VC++ was produced to make your CRC checking operations quick & easy to implement seamlessly without the need for an external DLL The CRC is a "digital fingerprint" of a file, With CRC32 you can "melt down" a huge 20 MB (or even much bigger) file to have a small, handy reference to it, a single 32-bit number like 7d9c42fb (hexadecimal notation) which would unambiguously reflect the entire contents of this huge file. Now if some changes to this file happened, no matter how small, maybe only a single wrong bit somewhere in the middle, a new CRC-32 calculation would yield a completely different reference number (say 3faa83bd). So there?d be no doubt about it - this is not the same file anymore. On the other hand if the reference number was still the same (7d9c42fb) you might be sure that the file hasn?t changed. The algorithm of CRC32 is exactly the same as that internally used by PKZIP and WinZip; i.e. the CRCs calculated by PKZIP and CRC32 are identical. That?s another fine thing about CRC32 - it calculates compatible, widely used 32-bit checksums, not just any numbers. You can use the 'pkunzip.exe -vt filename.zip' command to see that PKZIP?s CRC-32 values of files stored inside the filename.zip are identical to that calculated by CRC32 for these files. Though you can use CRC32 to calculate 32-bit checksums of any file the real strength and usefulness of CRC32 is in comparing Wave Sound Files to see if their non-silent music parts are identical. In particular CRC32 may come in handy when comparing two different extractions of a CD Digital Audio track to ensure that the performed digital copy is perfect.