What is the difference between a bug and an error

The first physically documented computer bug was documented by Dr. Grace Murray Hopper when she was programming the Mark II Calculator (computer). When the system was not functioning correctly after troubleshooting the system, she found a moth between contacts of a relay. After removing the moth the system functioned and the moth was taped in her notes documenting the bug.
A computer error is displayed when a known problem in the computer code (program) expects a result from the hardware (electronic circuit) or software, and it does not fall within the code parameters. In most cases the error can return information about why the computer had a problem.
Conclusion:
A bug is an unknown failure of the system which usually is intermittent and causes the system to crash or results in some type of failure. An error returns information about the system failure which is displayed or documented on the display or in log file.