Why Does Software Have Bugs?

All the Software Tester out there have a question in their mind “Why does Software have Bugs?”  and “How will these bugs occur?”. This question has been answered in this article.

In this article, we will be knowing the top 20 reasons why the Bugs occur in the Software. 

Software Have Bugs

What Is A Software Bug?

A Software Bug is a failure or flaw in a program that produces undesired or incorrect results. It’s an error that prevents the application from functioning as it should.

Why Does Software Have Bugs?

There are many reasons for Software Bugs. The most common reason is human mistakes in software design and coding.

Once you know the causes for Software Defects it will be easier for you to take corrective actions to minimize these defects.

software bugs

Top 20 Reasons For Software Bugs

#1) Miscommunication or No Communication

The success of any software application depends on communication between stakeholders, development and testing teams. Unclear requirements and misinterpretation of requirements are two major factors causing defects in software.

Also, defects are introduced in the development stage if exact requirements are not communicated properly to development teams.

#2) Software Complexity

The complexity of current software applications can be difficult for anyone without experience in modern-day software development.

Windows-type interfaces, Client-Server, and Distributed Applications, Data Communications, enormous relational databases, and sheer size of applications have all contributed to the exponential growth in software/system complexity.

The use of object-oriented techniques can complicate instead of simplifying a project unless it is well-engineered.

#3) Programming Errors

Programmers, like anyone else, can make programming mistakes. Not all developers are domain experts. Inexperienced programmers or programmers without proper domain knowledge can introduce simple mistakes while coding.

Lack of simple coding practices, unit testing, debugging are some of the common reasons why these issues get introduced at the development stage.

#4) Changing Requirements

The customer may not understand the effects of changes or may understand and request them anyway – redesign, rescheduling of engineers, effects on other projects, work already completed that may have to be redone or thrown out, hardware requirements that may be affected, etc.

If there are many minor changes or any major changes, known and unknown dependencies among parts of the project are likely to interact and cause problems, and the complexity of keeping track of changes may result in errors. The enthusiasm of engineering staff may be affected.

In some fast-changing business environments, continuously modified requirements may be a fact of life.

In this case, management must understand the resulting risks, and QA and test engineers must adapt and plan for continuous extensive testing to keep the inevitable bugs from running out of control.

#5) Time Pressures

Scheduling of software projects is difficult at best, often requiring a lot of guesswork. When deadlines loom and the crunch comes, mistakes will be made.

Unrealistic schedules though not common but the major concern in small-scale projects/companies results in software bugs. If there is not enough time for proper design, coding, and testing, it’s quite obvious that defects will be introduced.

#6) Egotistical or Overconfident People

People prefer to say things like:

  • ‘no problem’
  • ‘piece of cake’
  • ‘I can whip that out in a few hours’
  • ‘it should be easy to update that old code’

instead of:

  • ‘that adds a lot of complexity and we could end up making a lot of mistakes’
  • ‘we have no idea if we can do that; we’ll wing it’
  • ‘I can’t estimate how long it will take until I take a close look at it’
  • ‘We can’t figure out what that old spaghetti code did in the first place’
  • If there are too many unrealistic ‘no problem’s’, the result is software bugs.

#7) Poorly Documented Code

It’s tough to maintain and modify the code that is badly written or poorly documented; the result is Software Bugs. In many organizations, management provides no incentive for programmers to document their code or write clear, understandable code.

In fact, it’s usually the opposite: they get points mostly for quickly turning out code, and there’s job security if nobody else can understand it (‘if it was hard to write, it should be hard to read’).

Any new programmer starting to work on this code may get confused due to the complexity of the project and the poorly documented code. Many times it takes longer to make small changes in poorly documented code as there is a huge learning curve before making any code change.

#8) Software Development Tools

Visual tools, class libraries, compilers, scripting tools, etc. often introduce their own bugs or are poorly documented, resulting in added bugs.

Continuously changing software tools used by software programmers. Keeping pace with the different versions and their compatibility is a major ongoing issue.

=> Read more on Software Development Tools.

#9) Obsolete Automation Scripts

Writing automation scripts takes a lot of time especially for complex scenarios. If automation teams record/write any test script but forget to update it over the period of time that test could become obsolete.

If the automation test is not validating the results properly it won’t be able to catch the defects.

#10) Lack of Skilled Testers

Having skilled testers with domain knowledge is extremely important for the success of any project. But appointing all experienced testers is not possible for all companies.

Domain knowledge and the tester’s ability to find defects can produce high-quality software. Compromise on any of this can result in buggy software.

Here are a few more reasons for Software Bugs. These reasons are mostly applicable for Software Testing Life Cycle:  

#11) Not having a proper test setup (test environment) for testing all requirements.

#12) Starting to write code or test cases without understanding the requirements clearly.

#13) The incorrect design which leads to issues being carried out in all phases of the Software Development Cycle.

#14) Releasing software patches frequently without completing the Software Testing Life Cycle.

#15) Not providing training to resources for the skills needed for developing or testing the application properly.

#16) Giving very little or no time for Regression Testing.

#17) Not Automating Repetitive Test Cases and depending on the testers for manual verification every time.

#18) Not prioritizing test execution.

#19) Not tracking the development and test execution progress continuously. Last-minute changes are likely to introduce errors.

#20) The wrong assumption made while coding and testing stages.


There are many reasons why Software Bugs occur and the list of top 20 are mentioned in this article with a clear explanation of each reason.

Please feel free to share your thoughts in below comment section.

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70 thoughts on “Why Does Software Have Bugs?”

  1. i am working in telecom domain(OMCR) for past one year,but interested in testing how can i switch my field,but i have done a course in manual and automation testing..
    wat should i supposed to be done to get the job. i am B.E(ece) 2008 passed out…

  2. hi santosh this is inayath bbm graduate completed in 2008 and currently working in bpo for almost 1.6 yrs interested in testing but does not know anything about is it good to enter in to this field suggest me pls. And after completion of the course can i get job and which is the best institute in bangalore which provides placement and good training.

  3. Hi,

    Am an Engineer graduate(B.Tech IT), two years before i was working as a software engineer in an MNC, now i have become an housewife and now i would like to work from home. please let me know the process like how to start this job, kindly cntact me in 9841953176.

  4. sir

    Plz tell me any one my decision right or worng
    this is murthy i have 3 years exp in financial sector. i am mba holder. i am interested to learn testing is it correct decision. plz suggest witch inst is better in hyd?

  5. hi
    i m shweta . i m completed B.E.(I.T.). i m intrested in software testing so i m doing software testing course….
    if there are vacancies/opening for software tester plz plz …
    inform me on email id….

  6. hi…..
    How do you differentiate between client and server? Which tool do you use to detect any error in client server configuration?

  7. hi….
    How did you prepare a test case for Software Testing? What do you do if even after your software testing process an error is found

  8. Hi All Commerce graduate,

    Guy who r commerce graduate, n who having interest in Testing. They have got advantage in Bank and Finance domain projects.. So eventhough they are not from IT..they got chance in Testing as well…;)

    Do well Guys,



  9. Hi,
    i am completed BE electronics in june 2012. i have doute. can anyone tell me which option is peferable for me – software testing OR pgdwimc(cdac cours). i got 70% marks in final year.

  10. These are the few possible reasons for a software build to have bugs.

    1) When the product launch date is nearing, the developer skips one or two minor bugs and provides the software build to the testing team.

    2) When the developer misses out a bug by mistake and without checking the fixes, provides the software build to the testing team.

    3) Once the developer fixes the bug and does not check any other functionality of the software which has been changed or modified due to the fixation of the new bug and provides the software build to the testing team.

  11. hi,
    frnds many ask about testing oppotunities, first you people need to learn manual testing, after that prepare ur resume with effective nature about manual testing…….then search for jobs in internet …..any more about manual or automation leave a comment………

  12. Nice article to understand about bugs in softwares. People can understand how bugs are inserted into softwares and how they can be found. If one knows how bugs can be inserted in software, finding them becomes easy…

  13. AnyComputer Program contains a bug no matter how well it is programmed.
    The important here is that the program is run on processor which work is based on arithemetics. Hence Godel Theorem can be used.

    So, this means all computer programming is Sisyphus work.


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