(ABnormal END) An unexpected termination that causes the computer to stop responding. Also called a "crash," "bomb" or "lockup," an abend occurs when the computer 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).
Bad Hardware Can Look Like Bad Software
A serious hardware failure will stop a computer 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 crashproof, the computer locks up and has to be rebooted. Sophisticated operating systems attempt to halt only the offending application and allow the remaining applications to continue. As operating systems evolved through the years, they typically became more resilient to application bugs. There is less rebooting of the computer after an application crashes with newer versions of the OS than with older versions. The OS itself generally becomes more robust and crashes less often.
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 these days can easily have two billion memory cells. Every second, millions of them change their state from uncharged to charged and vice versa (0 to 1; 1 to 0). If only one cell fails, it can cause an instruction to be unrecognizable or an address to be invalid and results in an abend. See GPF and head crash.
Abending
Abending, or crashing, often occurs when the program points outside of its address space. This diagram depicts the anatomy of a program. "The Data" refers to constants used within the program and the input/output areas that hold the data while it is being processed. "The Processing" refers to the program's logic embodied in the flow chart and physically implemented as thousands of machine instructions (the columns).
Bad Hardware Can Look Like Bad Software
A serious hardware failure will stop a computer 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 crashproof, the computer locks up and has to be rebooted. Sophisticated operating systems attempt to halt only the offending application and allow the remaining applications to continue. As operating systems evolved through the years, they typically became more resilient to application bugs. There is less rebooting of the computer after an application crashes with newer versions of the OS than with older versions. The OS itself generally becomes more robust and crashes less often.
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 these days can easily have two billion memory cells. Every second, millions of them change their state from uncharged to charged and vice versa (0 to 1; 1 to 0). If only one cell fails, it can cause an instruction to be unrecognizable or an address to be invalid and results in an abend. See GPF and head crash.
Abending
Abending, or crashing, often occurs when the program points outside of its address space. This diagram depicts the anatomy of a program. "The Data" refers to constants used within the program and the input/output areas that hold the data while it is being processed. "The Processing" refers to the program's logic embodied in the flow chart and physically implemented as thousands of machine instructions (the columns).
 | Reproduced with permission from Computer Desktop Encyclopedia. Copyright (c) 1981-2008 The Computer Language Company Inc. All rights reserved. |
Additional Resources
- From Chapter one: Data Processing and the IBM Mainframe
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- From Chapter one: Data Processing and the IBM Mainframe
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- Discussion threads 2008-06-13
- One neck to choke
- One neck to chokeOn the other handLet's say you have Company A that decides to run WebSphere on top of AIX and Company B that decides to run WebSphere on top of RHEL. WebSphere is certified to run on both OSs.Now lets say you have an issue with an...
- Discussion threads 2007-10-04
- Ruling on Novell's Unix assets bolsters OSS, binds Novell and IBM
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- Discussion threads 2007-08-13
- Beta of Microsoft's antispyware tech falls short in tests
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- Discussion threads 2006-03-08
- Microsoft looks for 'protection' money
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