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Gaurav Prasad
Gaurav Prasad
Computer Science
25 Jan 2019

What is the difference between a Bug, Defect, Error, Failure, Fault, and Mistake?

give details?

Aswini Vi
Aswini Vi
Computer Science
1mo ago

The  terms-error,mistake,faults,bugs,failures, and defects are used interchangeably by the majority of people around the world,but they signify and represent different aspects of the software.

Error & Mistake :

During the process of software testing,errors are the most basic discrepancies found by the team of testers.These are the mistakes made by the software developer or programmer,while preparing the code or design of the software.Errors are mainly a deviation from the results expected by the team,which further changes the functionality of the software.

Reasons Error & Mistakes:

The reasons for these errors and mistakes are misconceptions or misunderstanding on the part of the software developer.Other reasons for errors and mistakes in the software are:

  1. Because of wrong login,loop,and syntax.
  2. Mistakes in the program.
  3. Confusion in understanding the requirements of the software.
  4. Miscalculation of some values.
  5. Misinterpretations and issues in coding.
  6. If a developer is unable to successfully compile or run a program.
  7. Mistakes in design or requirement activities.
  8. Discrepancy between actual and expected results.

Ways to Prevent Errors & Mistakes:

>> Improve software quality with code and system review.

>> Identify issues and prepare appropriate mitigation plan.

>> Verify fixes and validate their quality and accuracy.

>> Indulge in thorough testing.

>> Adopt effective software development methodologies.


Introduced in the software because of an error,fault is another discrepancy found by the team of testers during the process of software testing.Unlike error,the reason for a fault to occur while implementing the software is not because of a miscalculation of some value or discrepancy between actually and expected result,but is merely a manifestation of an error in a software.Moreover,a fault in the software system inhibits it from performing its intended function and forces the system to act in an unanticipated manner.

Reasons for Faults:

Faults in a system can be raised because of various reasons,few of which are mentioned here:

  1. Discrepancy in issue in the code that causes the failure of the system/program.
  2. Caused by an introduction of an incorrect step,process,or data definition.
  3. An anomaly or irregularity in the software ,which makes the software behave in an incorrect way and not as per the stated requirements.

Ways to Prevent Faults:

>> Implementing thorough code analysis.

>> Peer review.

>> Measure functional requirements.

>> Validate the accuracy of software design and programming.


Bugs are the most integral part of a software system and can be termed as the errors,flaws,and faults present in the computer program that impact the performance as well as the functionality of the software can cause it to deliver incorrect and unexpected results.These not only impact the performance of the software,but also cause it to behave in an unanticipated way.

Reasons for Bug:

From errors and mistakes made in the source code of the software,to issues and flaws found in the software design,the reasons for bugs to be introduced in the software system can be many,which are defined below:

  1. Error or flaw found in the development environment of the software.
  2. Issue in the software or hardware that it to malfunctions.
  3. Discrepancies in teh Operating System used by the program.
  4. Few bugs are even caused dure to incorrect codes produced by compilers.

Ways to Prevent Bugs:

>> Adapting innovative and defective development methodologies.

>> Offering programming language support.

>> Analyzing the code thoroughly.

>> Test-driven development.


When a software is incapable of performing the required functions and is offering results that are not adequate and far from the expected results,then it is termed as a failure.These failures are incorrect external behavior that leads a software to deliver services that are not in compliance with the specifications.

Reasons for Failures:

Failures usually occur when a defect present in the system is executed by the the team,which forces it to produce unpredicted and unanticipated results and function inappropriately.Other reasons that lead to the failure of the software are:

  1. Human Error: Errors and mistake made by the human while interacting with the software and by providing wrong or incomplete inputs.
  2. Environmental Conditions: Another common reason that forces the system to fail are the environment conditions.These impact the hardware and forces it to fail.Additionally,it changes the various environment variables.
  3. Users: Failures may also occur in the system if the user tries it perform operations that can harm the functionality if the software.Moreover,they can also execute actions with the intention of breaking the system,which will further lead to failures.
  4. System Usage: Failures might also arise due to errors in the way system is being used.

Ways to Prevent Failures:

>> Identify and analyze errors and issues.

>> Adopt effective preventive techniques.

>> Ensure re-testing.

>> Revise and revisit specifications and requirements.


If the actual result of the software deviates from the one expected and anticipated by the team of testers,while testing the software,then it results into a defect.Defects,are therefore,defined as any deviation or irregularity from the specifications mentioned in the product functional specification document by the client or any other stakeholders of the project.These are the discrepancies and issues in the software,found during the process of testing,that impact its functionality.Moreover,defects are error found after the application goes into product.

Reasons for Defects:

  1. An error in coding or logic that impacts the software and causes it to malfunction or perform in an inaccurate manner.
  2. Any deviation from the customer requirements also leads to defects in the software.
  3. Trouble and mistakes in the external behavior and internal structure and design.
  4. Providing wrong and inaccurate inputs.

Ways to Prevent Defects:

>> Peer review.

>> Adopting various efficient programming techniques.

>> Performing regular code reviews to assess its quality and accuracy.

>> Use of effective and accurate software development methodologies.

Though all these discrepancies-errors,mistakes,faults,bugs,failures,and defects -hamper the quality and performance of the software,but they influence and modify different parts of the software and vary from one another immensely.


AdhikariHarika Reshma
AdhikariHarika Reshma
Computer Science
1mo ago

@Aswini Variganji Thank you for explaining briefly.

Aswini Vi
Aswini Vi
Computer Science
1mo ago

Glad to know that you liked my post :)