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Thursday, February 23, 2012

What is meant by severity of a bug? What are different types of severity?

We all know what a software bug is! It is a flaw, error or mistake in the software system or application that can cause it to crash or fail. Pretty much simple!
But very few of us are actually aware about the severity of a bug i.e., how much destruction it can cause to a software system or application.

- Bugs are of course results of the mistakes made by the software programmers and developers while coding the software program.
- Sometimes incorrect compilation of the source code by the program can also cause bugs.
- A buggy program is very hard to clean.
- Bugs can have a chain reaction also i.e., one bug giving rise to another and that in turn giving rise to one more bug and so on.
- Each bug has its own level of severity that it causes to the software system or application.
- While some bugs can work out total destruction of the program, there are some bugs that do not even come in to detection.
- Some bugs can cause the program to go out of service.
- In contrast to these harmful bugs, there are other bugs which are useful such as security bugs.


-"Severity can be thought of as a measure of the harm that can be caused by a bug."
- Severity is an indication of how bad or harmful a bug is.
- The higher the severity of a bug, the more priority it seeks.
- Severity of the bugs of software can sometimes be used as a measure of its overall quality.
- Severity plays a major role in deciding the priority of fixing the bug.
- It is important that the severity of the bugs is assigned in a way that is logical and easy to understand.

There are several criteria depending on which the severity of a bug is measured. Below mentioned is one of the most commonly used ranking scheme for measuring severity of bugs:

1.Severity 1 Bugs
bugs coming under this category cease the meaningful operations that are being operated by a software program or application.

2.Severity 2 Bugs
Bugs coming under this category cause the failure of the software features and functionalities. But, still the application continues to run.

3.Severity 3 Bugs
Bugs coming under this category can cause the software system or application to generate unexpected results and behave abnormally. These bugs are responsible for inconsistency of the software system.

4.Severity 4 Bugs
Bugs coming under these categories basically affect the design of a software system pr application.

Severity has two main components namely the following:

1. Impact
- It is a measure of the disruption that is caused to the users when they encounter a bug while working.
- There is a certain level to which there is an interference with the user performing a task.
- Even the impact is classified in to various levels.

2. Visibility
- It is the measure of the probability of encountering the bug in future or we can say that it is measure of the closeness of a bug to the execution path.
- It is the frequency of the occurrence of a bug.

The severity is calculated as the product of both the impact as well as visibility. A measure of perceived quality and usefulness of the software product is given by the severity. Therefore it would not be wrong to say that the severity provides an overall measure of the quality of the software system or application.

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