crash

Crash or CRASH may refer to:

• Collision, an impact between two or more objects
• Crash (computing), a condition where a program ceases to respond
• Cardiac arrest, a medical condition in which the heart stops beating
• Couch surfing, temporarily staying at another person's home
• Gate crashing, the act of entering an event without invitation
• Stock market crash, a sudden dramatic decline of stock prices
• Crash (2004 film), directed by Paul Haggis and winner of the 2005 Academy Award for Best Picture
• Crash (card game), a British card game
• CRASH convention, a convention in the game of contract bridge
• Crash cymbal, used in occasional drumming accents
• Sugar crash, a supposed sense of fatigue after consuming a large number of carbohydrates
• A group of rhinoceroses
• A plain linen fabric used for towels
• Slang for comedown, the negative effect of a drug

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 exits. The program responsible may appear to hang until a crash reporting service reports the crash and any details relating to it. 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 executing invalid machine instructions. Typical causes include incorrect address values in the program counter, buffer overflow, overwriting a portion of the affected program code due to an earlier bug, accessing invalid memory addresses, using an illegal opcode or triggering an unhandled 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 code that actually crashed.

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

An application typically crashes when it performs an operation that is not allowed by the operating system. The operating system then triggers an exception or signal in the application. Unix applications traditionally responded to the signal by dumping core. Most Windows and Unix GUI applications respond by displaying a dialogue box (such as the one shown to the right) with the option to attach a debugger if one is installed. Some applications attempt to recover from the error and continue running instead of exiting.

An application can also contain code to crash after detecting a severe error.

Typical errors that result in application crashes include:

• attempting to read or write memory that is not allocated for reading or writing by that application (segmentation fault) or x86 specific (general protection fault)
• attempting to execute privileged or invalid instructions
• attempting to perform I/O operations on hardware devices to which it does not have permission to access
• passing invalid arguments to system calls
• attempting to access other system resources to which the application does not have permission to access
• attempting to execute machine instructions with bad arguments (depending on CPU architecture): divide by zero, operations on denormal number or NaN (not a number) values, memory access to unaligned addresses, etc.

A "crash to desktop" is said to occur when a program (commonly a video game) unexpectedly quits, abruptly taking the user back to the desktop. Usually, the term is applied only to crashes where no error is displayed, hence all the user sees as a result of the crash is the desktop. Many times there is no apparent action that causes a crash to desktop. During normal function, the program may freeze for a shorter period of time, and then close by itself. Also during normal function, the program may become a black screen and repeatedly play the last few seconds of sound (depending on the size of the data buffer) that was being played before it crashes to desktop. Other times it may appear to be triggered by a certain action, such as loading an area.

Crash to desktop bugs are considered particularly problematic for users. Since they frequently display no error message, it can be very difficult to track down the source of the problem, especially if the times they occur and the actions taking place right before the crash do not appear to have any pattern or common ground. One way to track down the source of the problem for games is to run them in windowed-mode. Windows Vista has a feature that can help track down the cause of a CTD problem when it occurs on any program. Windows XP included a similar feature as well.

Comedown or crashing is a phase of drug withdrawal that involves the deterioration in mood and energy that occurs when a psychoactive drug, typically a stimulant, clears from the blood. The improvement and deterioration of mood (euphoria and dysphoria) are represented in the cognitive schema as high and low elevations; thus, after the drug has elevated the mood (a state known as a high), there follows a period of coming back down, which often has a distinct character from withdrawal in stimulants. Generally, a comedown ("down", "low", sometimes "crash") can happen to anyone as a transient symptom, but in people who are dependent on the drug (especially those addicted to it), it is an early symptom of withdrawal and thus can be followed by others.

六级/考研单词: crash, collide, compute, sofa, surf, gradual, academy, convention, accent, fatigue, consume, carbohydrate, linen, hardware, seldom, panic, fatal, execute, valid, instruct, buffer, overflow, portion, affection, illicit, trigger, data, exploit, malignant, hack, arbitrary, virus, norm, dump, dialog, install, detect, allocate, segment, privilege, nil, desktop, quit, abrupt, freeze, deteriorate, mood, cognitive, thereby, elevate, transient, symptom