Understanding Software Bugs

Mojisola Otusheso
August 28, 2023

Software development is a complex and intricate process that often involves numerous lines of code and intricate algorithms. While developers strive for perfection, software bugs, also known as defects or glitches, remain an integral part of the development journey. Understanding these bugs and assessing their severity is crucial for delivering high-quality software. In this article, we delve into the world of software bugs, exploring their types, causes, and most importantly, how to evaluate their severity.


Functional Bugs:

These bugs occur when an application component fails to function as expected. For example, a button that doesn't respond or a login screen that doesn't authenticate users are common instances of functional bugs. This bug is an obstruction of user access.

Performance Bugs:

These bugs impact the entire application's operational efficiency such as the speed, stability, and response time. A performance bug occurs when the system's response time exceeds expectations. Slow response times, frequent crashes, or excessive memory usage fall under this category. These bugs can severely impact user experience.

Usability Bugs:

A user-friendly experience is pivotal in application development. Usability bugs occur when an application is challenging to navigate or lacks an intuitive user interface. For instance, a social media application that does not have a search bar. This would make it difficult for users to locate and connect with their contacts either through texting or calling. These bugs can discourage users from engaging with the software.

Compatibility Bugs:

Applications should ideally run across diverse devices, operating systems, and browsers. However, this is not always the case. With the vast array of devices, operating systems, and web browsers available, ensuring compatibility is a challenge. Compatibility bugs entail issues like font disparities, color inconsistencies, or misalignment.

Unit-Level Bugs:

After coding an application, developers assess its logical components through unit testing to ensure proper execution. Defects at the unit level include problems in state machines, miscalculations,and fundamental logic errors. Unit-level bugs can impact the core functionality of the software.

Security Bugs:

The security of an application is paramount. Security bugs expose vulnerabilities that hackers can exploit, endangering user information and system control. These bugs are among the most severe and demand immediate attention.

Syntax Bugs:

Syntax errors are prevalent in program source code, arising from missing code or improper characters. Examples include misspelled commands or absent brackets, which hinder the application's compilation process. Syntax bugs can prevent the software from compiling or executing correctly.


Software bugs can stem from various sources. See more on this article on who is to blame (Devs vs QAs). Some causes of bugs in software including:

Coding Errors:

Mistakes made by developers during the coding phase, such as logical errors or incorrect variable assignments.

Incomplete Requirements:

When requirements are unclear or incomplete, developers may inadvertently introduce bugs while attempting to fill in the gaps.

Poor Testing:

Inadequate testing, especially the absence of edge case testing or comprehensive test suites, can lead to undiscovered bugs.

External Factors:

Bugs can also be triggered by external factors such as hardware limitations, operating system updates, or third-party software interactions.


Assessing the severity of a software bug is essential for prioritizing its resolution. Here's a common approach to categorize bugs by severity:

High-Priority Bugs necessitate immediate attention upon discovery because they directly impact the application's functionality and performance. This encompasses issues like crashes or freezing, data corruption, or security vulnerabilities. High-priority bugs require immediate attention and often halt the release process.

Medium-Priority Bugs do not disrupt the core functionality but still affect the user experience or software performance. These may include performance issues, usability problems, or compatibility glitches. While not as urgent as high-priority bugs, they should be addressed promptly.

Low-Priority Bugs are minor issues that do not significantly impact the software's functionality or user experience. They may involve cosmetic defects, spelling errors, or non-standard behavior in edge cases. Low-priority bugs can be scheduled for resolution in future updates.

Mojisola Otusheso
When Moji indulges in her habitual daydreaming, she often finds herself transported to the vibrant landscapes of Mars; however, she seamlessly traverses between planets and devotes time to Earth as a diligent Quality Assurance specialist. Moji's fervor for exquisite cuisine, voracious appetite for reading, and insatiable wanderlust reflect her true passions.
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