hang

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hang

[haŋ]
(ordnance)
To lock the receiver or bolt of a gun in an open position.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

hang

(1)
To wait for an event that will never occur. "The system is hanging because it can't read from the crashed drive". See wedged, hung.

hang

(2)
To wait for some event to occur; to hang around until something happens. "The program displays a menu and then hangs until you type a character." Compare block.

hang

(3)
To attach a peripheral device, especially in the construction "hang off": "We're going to hang another tape drive off the file server." Implies a device attached with cables, rather than something that is strictly inside the machine's chassis.
This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)

abend

(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 become more bug-free themselves and more tolerant of application bugs. However, all operating systems are not 100% foolproof, and bad applications do cause operating systems to crash; a major motivation for virtualizing computers (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.



Abending
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 ?
"I hung tough the first eight holes - I was two over, but easily could have been three, four, five over the way I played.
But the close-knit Vietnamese-American community in the Crescent City hung together and hung tough, despite the city's effort to erect a trash-mountain landfill next to their neighborhood.
"When they took the lead we hung tough and did what we had to," Pacers coach Jim O'Brien said.
The Mil-Std generators have hung tough and many are still out there and being used.
The president hung tough, claiming the demonstrations had been arranged by student communist groups.
They hung tough for the first three sets of their loss to Banko Perlas until the fourth set where they fell apart.
Generika-Ayala hung tough down the stretch to eke out a thrilling 21-25, 25-22, 25-22, 26-24 win over PLDT Home Fibr on Tuesday and take their quarterfinal series in the Philippine Superliga Grand Prix to the distance at Filoil Flying V Centre in San Juan.
The Maroons hung tough in the crunch against the equally resilient Warriors with their sturdy net defense anchored on Millete and Ruskin Ijiran, who merged for eight of the team's 12 blocks.
Import Kanjana Kuthaisong and skipper Angeli Araneta came to the rescue of the Lifesavers, who hung tough down the stretch to eke out the thrilling win.
"We hung tough and that's really important for this group."
The Patriots (1-4) hung tough in the fourth quarter with a goal-line stand following first-and-goal from the 6.
"All credit to Hearts as they've hung tough but we know a win will qualify us for the UEFA Cup and that's a massive incentive.