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(computer science)
An unplanned program termination that occurs when a computer is directed to execute an instruction or to process information that it cannot recognize. Also known as blow up; bomb; crash.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


/o'bend/, /*-bend'/ ABnormal END. Abnormal termination (of software); crash; lossage. Derives from an error message on the IBM 360; used jokingly by hackers but seriously mainly by code grinders. Usually capitalised, but may appear as "abend". Hackers will try to persuade you that ABEND is called "abend" because it is what system operators do to the computer late on Friday when they want to call it a day, and hence is from the German "Abend" = "Evening".
This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)


(ABnormal END) Pronounced "ab-end." An abend is an unexpected termination that causes the computer, smartphone or tablet to stop responding. The abend occurs either when the processor is presented with instructions or data it cannot recognize, or a program tries to address memory beyond a defined boundary. Abends are generally the result of erroneous software logic in the application or operating system (see anomaly).

Crash, Freeze, Lock Up and Hang
A "crash" occurs when the computer issues a "fault" and deliberately halts that line of execution. The terms "freeze," "lock up" or "hang" may refer to software that is actually still running but has erroneously wound up in an endless, internal loop that renders the program useless. In practice, the terms "crash," "freeze," "lock up" and "hang" are used synonymously. See infinite loop.

Bad Hardware Can Look Like Bad Software
A serious hardware failure will stop a computer-based device that has no redundant components. For example, a short circuit on the motherboard will halt the operation; however, a failing memory cell can cause an instruction to point to an erroneous location, making it look like a software failure.

It Depends on the OS
If the abend occurs due to a bug in an application and the operating system is not resilient, the computer locks up and has to be rebooted. Modern operating systems attempt to halt only the offending application and allow the remaining applications to continue. As operating systems evolve through the years, they are more tolerant of application bugs. However, operating systems themselves are not 100% foolproof, and bad applications can cause operating systems to crash; a major motivation for running in a virtual mode (see virtualization and virtual machine).

A Miracle It All Works
If you consider what goes on inside a computer, you might wonder why it does not crash more often. An ordinary home computer can easily have 64 billion memory (RAM) cells. Every second, millions of them switch their status between charged and uncharged (1 to 0; 0 to 1). If only one cell fails, it can cause an instruction to be invalid, and an abend can occur. See head crash, GPF, active area and transistor concept.

The green blocks are machine instructions executed by the CPU one after the other until a branch (jump) instruction breaks the sequence and points to an instruction elsewhere in the program. Abending (crashing, hanging, etc.) occurs when the program erroneously points outside of its address space, typically due to bad logic.
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References in periodicals archive ?
The solution can automate much of the lower-level work, such as manually monitoring space allocation, and enable administrators to be more proactive, preventing many ABENDs. Easier diagnosis can significantly reduce the number of problems that require administrator intervention and can speed the resolution of escalated problems.
MAINVIEW SRM StopX37/II anticipates space shortages and proactively prevents or recovers from abends, allowing jobs to complete successfully the first time.
/ Abends sassen wir unter "Baumen / oder warfen Glanz uber die Cafetische." Like some postmodern Taugenichts, Jacobs finds his way in and out of lyric situations as if by chance, giving a luminosity to common language and to the ordinary moments of existence: "ein besonderer Wind in / besonders geformten Asten.
So too is Schnitzler's loneliness: 'Abends das Einsamkeitsgefuhl, das wohlbekannte' (2 December 1923).
In effect, my search for ABENDs was a precursor of those virtual reality pick-and-choose computer plots.
I used to get quite a few ABEND S 213s, which meant that a certain data set needed to run the program could not be found.
Geht der Durchschnittsverbraucher jedoch abends essen, zahlt er ungefahr 13,10 $.
Ungefahr 52% der Mahlzeiten (1,7 Milliarden) wurden in der Mittagszeit gegessen, 48% ara Abend. Insgesamt wurden 1999 nicht weniger als 9,8% aller italienischen Mahlzeiten nicht zu Hause eingenommen.