Illegal opcode in the context of Crash (computing)

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. On some operating systems or individual applications, a 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(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, 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 or unauthorized 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 triggered the crash.