A critical error is an error that causes a program to abort. A critical error might occur in an operating system, a running application, program or software. In this process, the operation that was being performed is aborted, and data may be lost. This may even result in freezing or spontaneous rebooting of the computer.

A critical error can be due to causes such as:

• An illegal instruction being attempted
• A program attempting to perform something which is impossible
• Invalid code being accessed

One of the most well-known critical errors in computing is the infamous Blue Screen of Death (BSoD) in Microsoft Windows operating systems.