A one-digit checksum.

Checkout Test language



["Checkout Test Language: An Interpretive Language Designed for Aerospace Checkout Tasks", G.S. Metsker, Proc FJCC 33(2) 1968].

Last updated: 1994-11-14



Saving the current state of a program and its data, including intermediate results, to disk or other non-volatile storage, so that if interrupted the program could be restarted at the point at which the last checkpoint occurred.

This facility came into popular use in mainframe operating systemss such as OS/360 in which programs frequently ran for longer than the mean time between system failures. If a program run fails because of some event beyond the program's control (e.g. hardware or operating system failure) then the processor time invested before the checkpoint will not have been wasted.

Last updated: 1995-02-07


<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.

Last updated: 1996-03-01

Nearby terms:

CHeap ASseMblercheapernetcheckdigitCheckout Test languagecheckpoint

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