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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 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.



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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lockup

A building or room for the temporary detention of prisoners by police.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.
References in periodicals archive ?
After the Akbari Gate custodial death incident, IGP Arif Nawaz ordered field officers, including CCPO BA Nasir, to ensure the installation of CCTV cameras in police lockups. It is important to note that CCTV cameras were installed where Zeeshan committed suicide.
Besides, CCTVs installed in police lockups are also functioning properly round the clock.
Ashfaq Khan said that the standard of facilities provided to criminals at lockups would also be improved by the effective monitoring system.
The report informed that the lockup has 402 additional prisoners beyond its capacity.
The death of a 16-year-old boy at a state of Texas lockup is now being investigated as a possible suicide, a Texas Juvenile Justice Department spokesman said Monday afternoon.
Speaking to Pakistan Today, the spokesperson of the Punjab University Khurram Shehzad said that the show-cause notices have been prepared and would be served to the students on Friday in their lockups through concerned police officials."The members of the disciplinary committee would be accompanied by legal advisors in the lockups of the suspended students to ensure justice," he said while adding that the university is bound to take a decision regarding the fate of the suspended students within 15 days otherwise their suspension would be overturned.
Dr Jeyaindran, who is in charge of medical services said that as a start, resident doctors will be placed at centralised lockups round-the-clock and eventually it will be extended to smaller lockups, the Malaysian Anti-Corruption Commission (MACC) lockups as well as Immigration detention centres.
rights and "new economy" asset lockups. And third, Delaware
Two years ago when asked in an interview on CNBC whether private equity was good for individual investors, Investure CEO Alice Handy said, "I understand why the industry would want to be in 401(K)s [but] it's sort of crazy for the average investor." She went on to point out that the illiquidity in private equity funds, where lockups can run as long as 10 years, high fees and lack of transparency and regulation.
In his opinion, Bouchard also dismissed allegations that Goldman Sachs & Co and Morgan Stanley had done anything wrong by collecting fees from Zynga when it lifted lockups for the executive investors.
| SIR - Barclay Sansom's article on keeping your valuables safe at summer music festivals ("There's a lot you can do to ensure thieves don't ruin your festival-going", June 8) contained some good advice, but omitted the best advice - if you're going to Glastonbury festival, use the free property lockups.
The first strand concerns IPO lockups. We use the IPO lockup event to distinguish the two hypotheses posited above and find that sales made by high ranking corporate insiders following IPO lockup expiration contain significantly negative information about their firm's valuation supporting the informative selling hypothesis.