What is an Error?

1. A discrepancy between expected and actual result.
2. The occurrence of an incorrect result produced by a computer.
3. An error is a difference between a computed, estimated, or measured value and the true, specified, or theoretically correct value.
4. In software engineering, the term error refers to an incorrect action or calculation performed by software as a result of a fault.
If, as a result of the error, the software performs an undesired action or fails to perform a desired action, then this is referred to as a failure.