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.

Recommended Reading

70 thoughts on “Why Does Software Have Bugs?”

  1. Hi
    I amworking in a leading bpo,these days i hear much about software testing career.can anybody help me in knowing how better it is to take this career………..

  2. Hi
    I am working as a techsupport executive in brigade i want a change in my career now days i am hearing more about testing tools that it has god opurtunities in that field i am a bsc graduate 2006 passed out so could you please suggest me what to do and please give the detail information about testing tools and where to learn and how to crack job, I am desperately in need of job as i am going to quit my current job………
    could you please e-mail me in detail about testing and how to crack job in short span of time.
    my E-mail ID: vamsi.kalepu@gmail.com
    Please help me to build my career as a test engineer

  3. hi
    from last four years i am working as a housewife. although a post graduate in computer science ,from hyd. I want a break in the software testing at hyderabad .how shall i get this opportunity. Moreover how shall i get acquaintence about the software testing in detail ,please mail me and guide .


  4. hi
    I am Commerce Graduate. i am intersted in IT. i complete my graduation in this year. can i do this course. right now i am doing C and C++ languege. is it possible or useful for me to make careere in this?
    right now i am working but it is some how related to IT as well as SAP. Please guide me. it is possible for comm graguate to make career in this field. i am in BPO section Backoffice. can u tell me the duration, fees, institution or other best or required thing which i dnt know. plz guide me for this

  5. Prajaktha i sincerely advice one thing as you are from commerce background i recommend you to go to finance side it is very difficult to survive in IT field according to the present situations so if possible learn acountiting packages and go in that direction. I know every one now a days looing farwrd to become a test engineer but it is very difficult. If you think that you that capability to go a head in this competition means i really wish u all the best for your commitement

    If you are hyderabad means u can take coaching from
    MIND Q or NAGESWARARAO both are in S.R NAGAR.
    course duration is 45 days and fee structure is 4000
    you should learn SQL SEVER also.
    any way all the best for your career.
    keep in touch and all the best once again.

  6. Hi seema,

    you did not mention your qualification. One thing i want to mention you seema that your are free with doing any job all these 4 years.
    To start a career as test engineer you have to make that 4 years as you worked some where untill unless you keep experience it is impossible to get a job.If you want to keep experience means u should be technically sound in Manual testing, tools like QTP AND LOAD RUNNER, and more over you should have good command over UNIX, SQL SERVER and ORACLE. I am not frightening you this is the basic fact you should know. To get command over this it takes not less than 1 year so once think upon this if you are really want to get into IT job then reoly me again i will give you the details.

    keep in touch

  7. I am a new software tester. could you please give me some example or documents link to learn about this.
    How can i get the proper document to write Test Script, Test Plan properly.

    thanks in advance

  8. Plz..I m working as a quality test engineer (6+ months), I really appreciate if you provide us the details of how to get this testing certifications done.

  9. Defect: When an error found by the test engineer (testing department) then it is called defect Or Defect is nothing but deviation from the requirement.

    Bug: if the defect is agreed by the developer then it converts into bug, which has to fix by the developer or post pond to next version. If am wrong pls let me know…..


  10. Hi JK
    Read this,
    BugBase–>A high quality software defect tracking tool. Very scalable so it’s useful for both small and large organisations. Highly configurable, integration with email, web based reporting etc.

  11. hi

    I want to get into this testing tools field, as i’m very passionate abt learning this, i’m learning testing tools from orbit, and also i’m completly from commerce background .I think that my keen passionate interest makes me survive in this field.

    But i want to know wht would be the scope for a fresher , which org’s r using this ,pls let me know the list of the org using it.

  12. Hi Devi,

    Very nice 2 here tat ur very interested in testng!
    Try with hope u will get. Pls mention all ur skils in ur cv. ok. all the best devi. pls forward to me i will do my best ok

  13. Hi jk, it means it only stores the bugs we have tracked and for purely communication purpose and to safely store details in server.Right!!!!!!!!

  14. Hi Devi,

    RapidTest Script Wizard, which is used in WinRunner, learns the application graphical user interface (which is abbreviated as GUI). It automatically creates a full suite of basic tests. The requirement of testers to create tests one at a time is reduced considerably. This is because the RapidTest Script Wizard walks through the application itself and reverse-engineers the test scripts directly from the application.

    The RapidTest Script Wizard learns all the objects or windows which are present in the application. The RapidTest Script Wizard basically performs two tasks. The first task which the RapidTest Script Wizard performs is it systematically opens the windows in your application and learns the description of every GUI object. The wizard then stores the information in a GUI Map file. The second task which the RapidTest Script Wizard performs is it automatically gene rates tests which are based on the information which it learns as it navigates through the application.

  15. Hi,

    Best of Luck, but becareful, plz donot put fake, if u put Fake experience also, try to maintain or else u will be def kicked…All the Best..

  16. Hi Friends,

    Currently i am working in Non-IT field and planned to switch my career to testing.I had learned the basics of testing,and now i am very eager to learn testing practically with real time projects.
    If any one interested to teach testing personally with real time projects , i will be more grateful, or else show me the right place in chennai.
    Thanks & regards

  17. hi,this is sandhya
    recently i completed my training in testing at vizag.
    the quieries asked in this site is being very useful to clarify our doubts regarding testing concepts.

  18. saw ur answers regarding testing tools i am appreciate a lot , can u help me out .
    Right now i am in australia pursuing diploma in computer field but not related to PR so i am deciding to comeback to india (some family problem) and do some course in testing tools what u think , i have some knowledge about computers i have done Bsc (2005) after that i am not taken any interested in doing job in india wasting my precious time by going abroad. I am 29 now i am sorry what i have done. Can u please suggest me that its good to do testing tools on this age.But i know that its difficult for me to go form the scratch but i can do, if u suggest good reply for my future.
    By reading all this u get the idea what guy i was,from the bottome of my heart i am very regret what i have done, Now i am realised that how important the career is please please suggest me what to do , i am interest in computers field.
    Thanks for ur preciuse by reading this.
    One important think my english also not so good .

  19. hi everyone, am working as test engineer.can anyone give me solution for testing latitude and longitude text boxes. there is no validation provided by the developers.

  20. hi
    I am Commerce Graduate. i am intersted in software testing. i complete my graduation in 2005. can i do this course. right now i am working in SAP as Account Assistant in MUMBAI. is it possible for me to make careere in this?
    Please guide me. it is possible for comm graguate to make career in this field. Can u tell me the duration, fees, institution or other best or required thing which i dnt know. plz guide me for this

  21. Hiii
    I m Dhanashree.. i m Comm graduate. and had completed Software Testing Course in jan2009 from COEP Coll. pune.. but till the date I didnt get job. so please anybody know about vacancies for tester in Pune. please inform me..
    Thank You

  22. Hi,
    iam maheshwari.i completed MCA.after that i wasted my time bcs i dont have proper guidance to do job.also iam poor in english.from two years onwords iam searching on testing tools even i didnt get job still now.i attended so many interviews after 4 rounds also i rejected.like this i rejected everywhere.now iam in depretion.i dont know when will i get job.pls give me any suggestions .icant leave this bca i paid 1lakh thatsy.

  23. Hello Maheswari,

    Donot loose hope or confidence. First thing what the managers see is that whether ur CONFIDENT or not. And now the market is RISING UP, so, it is time for u to get ajob also. If u want any help ormore suggestions, i am ready to help u. ofcourse i am in this field for almost 6+ yrs and working in MNC’s: santoshpalvai@yahoo.com, Best of luck for ur future

  24. hi

    actually i’m working on manual testing in delhi from last 1.3 years…i’ve done testing certification als0
    Now i want to switch to pune…
    if u guys hav any info about any opening in pune(in testing) plz let me know


  25. hai,
    I have 2+ year experence for client site(NIC-National informatic center) in chennai. my nature of work: application maintaince and train to all staffs…
    so now i’m looking for s/w testing…so how to prepare the testing interview and…. how to mention my experence..
    so how to prepare my CV… Give me idea……….

  26. hie guyz..murlee here..right now am working with reliance BPO as a CSR(techSupport)..completed my 6mnths there…but am not intrested in this field..am not made for serving customers..i am a Bsc (IT) student..appearing for my last sem this April-2010…want a career in SoftwareTesting..pls guide me how to achieve it..after graduation am planning to do PG in MCA..but donno whther i will break the MHT-CET..pls tell me everything on how to get this done..what shld i posses for the same..wht is the limit of the course..is it Worth doing..

Leave a Comment