Crash* (computing) Crashing** A crash (or system crash) in computing is an event in which a computer or a program (such as a software application or an operating system) ceases to function properly, often exiting after encountering errors. The program responsible may appear to freeze or hang until a crash reporting service documents details of the crash. If the program is a critical part of the operating system kernel, the entire computer may crash, often resulting in a fatal system error. Many crashes are the result of the execution of single or multiple machine instructions. Typical causes are when the program counter is set to an incorrect address or a buffer overflow overwrites a portion of program code due to an earlier bug. In either case, it is common for the CPU to attempt to execute data or random memory values. Since all data values are possible but only some values are valid instructions, this often results in an illegal instruction exception. By chance, such data or random values could be valid (though unplanned) instructions. The original program problem (software bug) is considered what caused the crash, but the actual fault was an illegal instruction. The art of debugging such crashes is connecting the actual cause of the crash with the code that set off the chain of events. This is often very far from obvious—the original bug is usually perfectly valid code to the processor. In earlier personal computers, it was possible to cause hardware damage through attempting to write to hardware addresses outside of the systems main memory. The execution of arbitrary data on a system will result in a breakup of screen display. This is widely considered a severe system crash.
Posted on: Mon, 04 Nov 2013 05:20:55 +0000
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