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2019-07-08T15:10:57Z

Created page with "The '''SYSV checksum algorithm''' is a commonly used, legacy checksum algorithm. It has been implemented in UNIX System V and is also available through the sum (Uni..."

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The '''SYSV checksum algorithm''' is a commonly used, legacy [[checksum]] algorithm.
It has been implemented in [[UNIX System V]] and is also available through the [[sum (Unix)|GNU sum]] command line utility.

==Newer checksum algorithms==
The manual page of the GNU sum utility program (that implements the [[BSD checksum]] algorithm) states:
"sum is provided for compatibility; the cksum program is preferable in new applications."

==Description of the algorithm==
The main part of this algorithm is simply adding up all bytes in a 32-bit sum. As a result, this algorithm has the characteristics (disadvantages and advantages) of a simple sum:
* re-arranging the same bytes in another order (e.g. moving text from one place to another place) does not change the checksum.
* increasing one byte and decreasing another byte by the same amount does not change the checksum.
* adding or removing zero bytes does not change the checksum.
As a result, many common changes to text data are not detected by this method.

The last two lines of the algorithm reduce the total sum to a 16-bit number.

==Sources==
* [https://www.gnu.org/software/coreutils/manual/html_node/sum-invocation.html official GNU sum manual page]
* [https://www.gnu.org/software/coreutils/ coreutils download page] --- find and unpack the newest version of the coreutils package, read src/sum.c

==Source==

[http://wikipedia.org/ http://wikipedia.org/]
[[Category:Checksum algorithms]]
==See Also on BitcoinWiki==
* [[Soundeon]]
* [[Zonafide]]
* [[DCoin]]
* [[Ligercoin]]
* [[Datareum]]

SYSV checksum - Revision history

Admin: Created page with "The '''SYSV checksum algorithm''' is a commonly used, legacy checksum algorithm. It has been implemented in UNIX System V and is also available through the sum (Uni..."