Difference between Bug, Defect and Error:

Bug – When the software does not perform as expected.
Defect – When the software has a undesirable feature.
Error – When the software deviates from the correct value.

Bug:
- Things the software does that it is not supposed to do.
- Something the software doesn’t do that is supposed to do.
- A fault in the program which causes the program to perform in an unintended or unanticipated manner.

Defect
- A product anomaly.
- Non-conformance to requirements.
- A quality problem discovered after the released to end user.

Error
- A discrepancy between computed, observed or measured value or condition and the true, specified or theoretically correct value or condition.
- A quality problem discovered by the S/W engineers (or others) before the software is released to the end user.

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