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For all those who really want an explanation, a checksum is a numerically calculated value which has taken some specific file information such as create date etc, and added a calculated value shich performs specific arethmitic calculations on each byte of the code, to create a unique number.
It is used in software to insure that the software is original and not corrupted.
It is used in communications, to insure that messages are transmitted without error.
In some instances, depending on the technuique employed it can be used for error correction of transmitted data.
If you change one line of code in several megabytes of a program, it will usually generate a different checksum.
As a result, V1.1, 1.2 and 1.3 of the K10D software (for example) each have different checksums, and if there is an error in loading the software this is the first way the camera detects it. The checksum is downloaded as part of the software loading process, and compared with the calculated value the camera makes. The probability of having an error in the checksum as it is downloaded, and an error that produces the same erroneous checksum, or multiple errors that result in the calculation of a valid chechsum is very very low.
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