11 Types of Software Bugs Every Developer Needs to Know

Software bugs are inconvenient and potentially expensive. Learn the different types of software bugs and how to fix them here. 

Today, software teams face a large amount of pressure to write massive lines of code, quickly, efficiently, and to meet each business and customer requirement. Add to this the fact that projects today are becoming more complex, and software bugs are bound to happen, regardless of how careful or skilled a developer may be. 

Software bugs can range from common and relatively simple, such as an unclickable button that doesn’t save a customer’s email address, to serious security concerns that can halt an upcoming release or completely alter program behavior. These programming errors can result in serious financial losses and seriously damage a company’s reputation.  

Whether the bug is commonplace or a more serious software error, they are going to happen during the development life cycle of your project, but that doesn’t mean you need to fear them. By being aware of these 11 types of software bugs and utilizing different types of testing, you and your software development staff or team can help to ensure that your next project is bug-free and reaches full customer satisfaction. 

What is a Software Bug? And Why Do They Matter?

According to Wikipedia, a software bug is an “error, flaw, failure, or fault in a computer program or system that causes it to produce an incorrect or unexpected result, or to behave in unintended ways.” It’s possible that the term “bug” was coined by computer programmer Grace Hopper in 1947 after she found a dead moth in the relay of Harvard University’s Mark II electromechanical computer. Or it may go back even farther, all the way to Thomas Edison who used the term while working on the quadruplex telegraph system in 1873.  

Regardless of the term’s origin, software bugs happen when there is a mistake made in the source code, components, or operating system of a program. Some, such as a recent iPhone bug that left users unable to type the letter “i”, are relatively harmless. Others can be expensive, like the reportedly $100 billion spent to fix the Y2K bug. And, still, other types of software bugs can be deadly, such as the Patriot missile bug in 1991 that led to the death of 28 people.

Software bugs and bug management matters for several reasons. First, most software developers and programmers want to create quality code. That is the calling code of their profession. Any code that is buggy reflects poorly on them and their team, and will ultimately affect the business’ bottom line. Secondly, buggy code is difficult to work with and hinders productivity. The more you can write quality code, the more effective you can be. Finally, bugs are costly. It is estimated that different types of software bugs cost the world economy $1.7 trillion dollars in 2017.

Even if it may not cost your company trillions of dollars, the cost of a bug increases as it progresses through the software development life cycle. According to IBM’s Systems Sciences Institute, the cost to fix a buggy release was four to five times greater than a software bug discovered during the design phase and up to 100 times greater than a defect found in the maintenance phase. And these costs don’t only apply internally. IBM also reported that software bugs can cost an average of $2.3 billion in shareholder value on the very first day it is made public. 

11 Types of Software Bugs

There are several different types of software bugs that you may encounter during your development career, but here are 11 of the most prevalent types. 

  1. Functional errors

    When it comes to functionality, each program should work correctly, but sometimes it doesn’t. When the software does not act as it is intended, this is a functionality error. Functionality errors are a broad category of errors and can range from basic functionalities, such as simple buttons that are unclickable, all the way up to the inability to use the main functionality of the software. A functional error is usually found via functional testing. After the functional testing, software testers may discover a more specific software bug behind the functionality error and may then reclassify it as one of the other types of software bugs.

  2. Performance defects

    Another of the types of software bugs, performance defects are tied to the software’s speed, stability, response time, and resource consumption. This type of bug is discovered during the performance testing phase of the software development process. One of the more common types of software bugs, performance defects include a software that runs at a slower speed than required or a response time that is longer than acceptable for the project’s requirements.

  3. Usability defects

    A usability defect is a type of error that hinders a user from using the software to its fullest capability. This bug makes a piece of software difficult or inconvenient to use. Examples of usability defects include a complex content layout or a signup feature which is too complicated. In order to discover these types of software bugs, software engineers and UX designers must check their software against the Web Content Accessibility Guidelines and other usability requirements during the usability testing phase.

  4. Compatibility defects

    Compatibility errors occur when an application does not perform consistently on different types of hardware, operating systems, browser compatibility, or when performing with particular software under formal specifications. These compatibility bugs may not necessarily be discovered during general software testing. Instead, compatibility testing must take place in order to discover these types of software bugs. An example of compatibility bugs in software could be a defect related to font size, color or alignment. The font may display perfectly in one web browser, but may be the wrong size in another.

  5. Security defects

    Security bugs are perhaps one of the most serious types of defects that a software developer or software engineering team can come up against. Security errors may be slightly different from other types of software bugs in that they make your project vulnerable. A security bug opens your software, your company, and your clients up to a serious potential attack. And these attacks can be costly, especially for smaller businesses. Companies with fewer than 500 employees incurred losses of more than an average of $2.5 million due to data breaches, an absolutely devastating amount for small and midsize organizations.

    The Open Web Application Security Project (OWASP) lists ten security risks, but some of the most common are encryption errors, susceptibility to SQL injections, XSS vulnerabilities, buffer overflows, logical errors, and inferior authentication, among others.

  6. Syntax errors

    These types of software bugs occur in the source code of a program. Syntax errors are one of the more common software bugs and will prevent your application from being compiled properly. This type of issue happens when your code is missing or has incorrect characters. A misspelled command or missing bracket are examples that could cause this software defect. Your development team will typically become aware of these errors through the use of compiling programs.

  7. Logic errors

    Logic errors is one of the types of coding errors that can cause your software to produce the wrong output, crash, or even software failure. Logic defects are an error in the flow of your software, such as an infinite loop. The infinite loop happens due to badly written or wrong coding which causes the program to malfunction and forces a certain sequence to repeat forever, until the program either crashes or there is some outside interruption, such as closing the program or turning off the power.

  8. Unit-level bugs

    Another of the most common types of bug is the unit-level software bug. Once your program has been coded, agile teams and other software developers typically perform unit testing, testing out a smaller section of the code as a whole to ensure that it works as it should. It is during this testing process that teams will start to discover unit-level bugs, such as calculation errors and basic logic bugs. Because you are still only dealing with a relatively small amount of code, these unit-level types of software bugs are easier to isolate and fix.

  9. System-level integration bugs

    These errors happen when there’s a mistake in the interaction between two different subsystems. These types of software bugs are generally more difficult to fix because there are multiple software systems involved, often written by different developers. System-level integration bugs occur because there is almost always a certain level of clarification that is needed in regard to the actual requirements, despite how solid the software requirements may appear to be. Examples of these bugs include byte-swapping, message parsing, and memory overflow defects.

  10. Code Duplication

    This defect occurs when a sequence of code occurs more than once. This can mean that lines of code are literally duplicated, character for character, but it can also apply to code that has the same tokens. In this case, the lines of code can look and act completely differently, but the actual functionality may render identical results. Code duplication can be a problem for several reasons. The extra coding can cause your program to become bulky, slowing down your product functionality. And today every millisecond counts. It also decreases your code quality, making your code smelly and increasing your technical debt.

    In order to avoid code duplication and becoming a smelly programmer, practice the DRY Principle: Don’t Repeat Yourself. Stay away from duplicate code as much as possible and take advantage of a software solution like Sider Scan to help you maintain high-quality control.

  11. Data Type Mismatch

    This is another of the most common software defects. When one of these software flaws occurs, it is because the wrong data type has been assigned to a variable or parameter. An example is when special characters are allowed in a name field or letters and numbers have been swapped incorrectly. These errors must be located and corrected. 

Are Software Bugs Always Bad? 

While we’re not encouraging you to accept or ignore these types of software bugs, the fact is that bugs are inevitable in coding. Each error in software can possibly provide some positive potential for you as a software developer. 

Each mistake that happens is a chance for you to learn and improve in your programming. If, while performing different testing types or code analysis, your tester is able to break the program in an unforeseen way through unanticipated user input, this shows you something you may have otherwise missed about your end-user. If you find compatibility defects, you now know to build your application around that issue. If you perform software testing and a bug slips through, you now know that you can try new software testing approaches. 

Bugs happen for a number of reasons, but often because of human error. These bugs help to show you where you can continue to improve as a coder. If you made an assumption about the code, you now know not to make that assumption again. You know where you may need to brush up on certain skills. Software bugs can show you this. 

Additionally, many types of software bugs occur due to a lack of communication. Today, projects are becoming more complex and moving faster than ever before, and this requires increased communication between teams in an organization, as well as team members within the agile teams. And, let’s face it, many software engineers would rather learn about the latest technologies than communicate with others. 

But in order for a project to flow smoothly, efficiently, and on time, team members must communicate. As you communicate with different members of your team, as well as the quality assurance team, you can help avoid programmer confusion and will learn even more about your project, as well as real user conditions. After all, software is designed by developers and programmers, but will be used by other people. That’s why it is critical to communicate and learn how those others will actually use the product. 

Software bugs can be anything from syntactic errors or an incorrect formula to a serious defect in one of your program’s security features. It’s important to remember that these types of errors are going to happen throughout your career.

But, as you continue to grow your skills and improve your communication, you may find that you become an overall much better software developer and that each software project improves as you deal with these different types of bugs.

If you approach these types of bugs as an interesting challenge, you and your software development staff may start to look at them in new ways. Through bug tracking and testing, you’ll start to learn what is essential to your program and what is not. In this way, you’ll begin to go beyond extra features and applications, and, instead, may begin to focus on the core necessities and use cases of your program, resulting in increased customer satisfaction, greater product functionality, and becoming an overall better software developer. 

How Can Sider Scan Help You? 

Sider Scan finds one of the most difficult types of bugs which are based on code duplication. When code is duplicated and then later modified, other duplicates also require the same modifications. These series of changes lend itself to software bugs being generated, and these types of bugs are extremely difficult to find, if not impossible as the codebase grows. Sider Scan is available for free for a single project. It is a proprietary duplicate code detection tool that is more flexible and faster than those in the market. See what kind of bugs it can find for you.

Aki Asahara

CEO of Sider. Aki joined Fixstars in 2008 and served major clients such as the US Airforce, MIT, USC, Toyota, and Hitachi High-technologies. After his successful tenure, he was appointed CEO of US operations in 2012. He was appointed CEO of Sider in 2019. He holds a Ph.D. in Astrophysics from Kyoto University and is a Certified Scrum Master.

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