error

The difference between the expected and the actual.

In computing, the way that the operating system reports unexpected, unusual, impossible, or illegal events is by displaying an error number or error message. Errors range from trivial, such as an attempt to write a file to a disk drive that does not contain a disk, to fatal, such as when a serious operating system bug renders the system useless.

In communications, errors are often caused by line noise and signal distortion. Parity or cyclical redundancy check (CRC) information is often added as overhead to the data stream, and techniques such as error detection and correction are employed to detect and correct as many errors as possible.

See also attenuation; crosstalk; error handling; error message; error rate; parity error.