Checksum

Checksum is a technique whereby the individual binary values of a string of storage locations on your computer are totalled, and the total retained for future reference. On subsequent accesses, the summing procedure is repeated, and the total compared to that derived previously. A difference indicates that an element of the data has changed during the intervening period. Agreement provides a high degree of assurance (but not total assurance) that the data has not changed during the intervening period.

A check sum is also used to verify that a network transmission has been successful. If the counts agree, it is safe to assume that the transmission was completed correctly.