Editing Crash (computing) (section)

{{Short description|Unexpected program exit due to an error}}
{{Redirect-distinguish|System crash|System Crash (TV series)}}
{{Use dmy dates|date=December 2024}}
{{more citations needed|date=December 2013}}
[[File:Crashed computer.jpg|thumb|A [[kernel panic]] displayed on an [[iMac]]. This is the most common form of an operating system failure in Unix-like systems.]]

In [[computing]], a '''crash''', or '''system crash''', occurs when a computer program such as a [[software application]] or an [[operating system]] stops functioning properly and [[exit (system call)|exits]]. On some operating systems or individual applications, a [[crash reporter|crash reporting service]] will report the crash and any details relating to it (or give the user the option to do so), usually to the [[Developer (software)|developer(s)]] of the application. If the program is a critical part of the operating system, the entire system may crash or hang, often resulting in a [[kernel panic]] or [[fatal system error]].

Most crashes are the result of a [[software bug]]. Typical causes include accessing invalid memory addresses,{{efn| name=invaddr|Types of invalid addresses include:
* Invalid real address
* [[Segmentation fault|Invalid segment number]]
* [[page fault|Invalid page number]]
* Address not on correct boundary (alignment error)
}} incorrect address values in the [[program counter]], [[buffer overflow]], overwriting a portion of the affected program code due to an earlier bug, executing invalid [[machine instructions]] (an [[illegal opcode|illegal]] or [[Protection ring#Supervisor mode|unauthorized]] opcode), or triggering an unhandled [[Exception handling|exception]]. The original software bug that started this chain of events is typically considered to be the cause of the crash, which is discovered through the process of [[debugging]]. The original bug can be far removed from the [[source code|code]] that actually triggered the crash.

In early personal computers, attempting to write data to hardware addresses outside the system's main memory could cause hardware damage. Some crashes are [[Exploit (computer security)|exploitable]] and let a malicious program or [[hacker]] execute [[arbitrary code execution|arbitrary code]], allowing the replication of [[computer virus|viruses]] or the acquisition of data which would normally be inaccessible.