## calcfilecrc32

To ensure that a downloaded file has not been changed during transmission use [calcfilecrc32] to calculate the CRC32 value the file.

`[calcfilecrc32 file=checkthisfile.txt]`

The result is a value in bits.CRC32 is a 32-bit Cyclic Redundancy Check code, used mainly as an error detection method during data transmission. If the computed CRC bits are different from the original (transmitted) CRC bits, then there has been an error in the transmission. If they are identical, it can be assume that no error occurred (there is one chance in 4 billion that two different bit streams have the same CRC32). The idea is that the data bits are treated as a data polynomial and the CRC bits represent the remainder of the division of the data polynomial by a fixed, known polynomial (called the CRC polynomial).

**From WebDNA v8.1**, to calculate the CRC32 of a string, use [calcfilecrc32][string][/calcfilecrc32]