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(storage, communications)
A computed value which depends on the contents of a block of data and which is transmitted or stored along with the data in order to detect corruption of the data. The receiving system recomputes the checksum based upon the received data and compares this value with the one sent with the data. If the two values are the same, the receiver has some confidence that the data was received correctly.

The checksum may be 8 bits (modulo 256 sum), 16, 32, or some other size. It is computed by summing the bytes or words of the data block ignoring overflow. The checksum may be negated so that the total of the data words plus the checksum is zero.

Internet packets use a 32-bit checksum.

See also digital signature, cyclic redundancy check.


A value used to ensure data are stored or transmitted without error. It is created by calculating the binary values in a block of data using some algorithm and storing the results with the data. When the data are retrieved from memory or received at the other end of a network, a new checksum is computed and matched against the existing checksum. A non-match indicates an error.

Just as a check digit tests the accuracy of a single number, a checksum tests a block of data. Checksums detect single bit errors and some multiple bit errors, but are not as effective as the CRC method. Checksums are also used by the Sophos antivirus software to determine if a file has changed since the last time it was scanned for a virus. See ECC memory and Sophos.
References in periodicals archive ?
TTI accountants have laboriously calculated and provided some numbers that you can use to check your output--these check-sums are provided after most queries and usually consist of the first few rows of the output you should expect to get; for those queries without check-sums, you'll need to do some checking on your own to validate your results.
NexentaStor capabilities include: -- Unlimited incremental backups with integrated search to manage these backups -- A full suite of back-up and replication capabilities, including syncing, cloning, and block level mirroring -- Industry leading data integrity due to end to end check-sums and other capabilities -- 15 minute installations via wizard led installation and provisioning -- One-touch safe upgrades, using advanced packaging solutions and ZFS in the kernel -- Inherent, file system level thin provisioning and storage virtualization, saving capacity costs and improving performance through I/O pooling -- Freedom from capacity based pricing
The agent remains accurate by comparing the check-sums of the installed files with those on the server.