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Please give me exact definition of error, bug, defect, fault and failure with some examples?

Please give me exact definition of error, bug, defect, fault and failure with some examples??????

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Hi Richa sharma,

       Error:This is a part of a system state that is liable to lead to a failure.With respect to fault it is a manifestation of a fault in a system.User errors are not part of the above error definition.A user error is a mistake made by a user when operating a software system.The system is able to react to this mistakes,because it is designed to expect such situations and it is the part of the required functionality.The handling of those situations,which of course can be abnormal,should be treated in the user interface component of the system .In contrast to an error,a user error cannot result in a system crash,but like a system error,a user error normally can result in an exception raised by a system component.


           Bug:Software is said to have a bug if it features deviates from specification.


           Defect:In software testing a defect is considered to be anything that can hamper the functioning or execution of the software application   or  service .The defect can be either a failure of a certain section of the code to function accurately,a flaw in the design of the system, or a fault,which could either be an error in the program.


           Fault:A fault is the origin of any misbehavior.It is adjudged or hypothesized cause of an error.


            Failure:A failure is a deviation of the delivered service from compliances with  the specification.Whereas an error characterizes a particular state of a system,a failure is a particular event namely the transition from correct service delivery to incorrect service.



lakshmi kanth reddy

Hi lakshmi kanth reddy,


Thanks for explantion..gud answer




Hi Vishnu,

Error is fine..

but BUG is something called which is found at testing end and defect is found after software/application goes on production server.


Guys as of my knowledge, Even though all have similar meanings it differs as


  • Error: Which is done by human mistake.. In programming
  • Defect: Deviation from the Requirement(s), Testers will raise defects
  • Bug: If the Defect was accepted by Developer, it will be a bug
  • Fault: If major Functionality Missed after delevering
  • Failure: If Customer identifies it is failure.

Read this article on this link to understand difference between Error, Bug, defect, fault and failure



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