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# Cyclomatic Complexity: What It Is, How to Calculate It, and Why It Matters

## Tool For Control Flow Of Cyclomatic Complexity: A Software Metric for Measuring Code Complexity

Code complexity is one of the most important aspects of software quality. It affects the readability, maintainability, testability and reliability of a software program. Code complexity can be measured by various metrics, but one of the most widely used and accepted ones is the cyclomatic complexity. In this article, we will explain what cyclomatic complexity is, how it can be calculated using a tool for control flow of cyclomatic complexity, and why it is useful for software testing and development.

## What is Cyclomatic Complexity?

Cyclomatic complexity is a software metric that measures the number of linearly independent paths in a program's source code. It was proposed by Thomas J. McCabe in 1976 as a way to quantify the complexity of a program based on its control flow structure. Control flow is the order in which the instructions of a program are executed. It can be represented by a graph, where each node corresponds to an instruction or a block of instructions, and each edge corresponds to a possible transition from one node to another.

The cyclomatic complexity of a program is equal to the number of regions in the control flow graph, or equivalently, the number of edges minus the number of nodes plus two. The cyclomatic complexity can also be calculated by counting the number of decision points (such as if statements, loops, switches, etc.) in the code and adding one. The higher the cyclomatic complexity, the more complex the program is.

## How to Calculate Cyclomatic Complexity Using a Tool For Control Flow Of Cyclomatic Complexity?

To calculate cyclomatic complexity using a tool for control flow of cyclomatic complexity, we need to first generate a control flow graph from the source code of the program. There are various tools and frameworks that can help us with this task, such as OCLint for C and related languages, Reflector Add In for .NET assemblies, GMetrics for Java related applications, etc. These tools can parse the source code and create a graphical representation of the control flow structure.

Once we have the control flow graph, we can apply the cyclomatic complexity formula to it and obtain the value of the metric. Alternatively, we can use tools that can directly calculate cyclomatic complexity from the source code without generating a control flow graph, such as Lizard for Python and C/C++, Code Metrics PowerTool for Visual Studio projects, etc. These tools can scan the source code and report the cyclomatic complexity value for each function, module or class.

## Why is Cyclomatic Complexity Useful For Software Testing and Development?

Cyclomatic complexity is useful for software testing and development because it provides an objective measure of how complex a program is. By knowing the cyclomatic complexity of a program, we can estimate how difficult it will be to test, debug and maintain it. Generally speaking, programs with lower cyclomatic complexity are easier to test and understand than programs with higher cyclomatic complexity.

Cyclomatic complexity can also help us design better programs by guiding us to avoid unnecessary complexity and refactor our code when needed. A common rule of thumb is to keep the cyclomatic complexity below 10 for each function or module. If the cyclomatic complexity exceeds this threshold, we should consider splitting the function or module into smaller and simpler units.

Cyclomatic complexity can also help us achieve better test coverage by indicating how many test cases are needed to cover all possible paths in a program. Test coverage is the percentage of source code that is executed by a set of test cases. A higher test coverage means that more defects are likely to be detected and fixed before releasing the software. Cyclomatic complexity can be used as an upper bound for test coverage, since it represents the maximum number of independent paths in a program.

## Conclusion

Cyclomatic complexity is a software metric that measures the number of linearly independent paths in a program's source code. It reflects how complex a program is based on its control flow structure. Cyclomatic complexity can be calculated using a tool for control flow of cyclomatic complexity that generates a control flow graph from the source code or directly scans the source code. Cyclomatic complexity is useful for software testing and development because it helps us estimate how difficult it will be to test, debug and maintain a program, design better programs by avoiding unnecessary complexity and refactor our code when needed, and achieve better test coverage by indicating how many test cases are needed to cover all possible paths in a program.

## Conclusion

Cyclomatic complexity is a software metric that measures the number of linearly independent paths in a program's source code. It reflects how complex a program is based on its control flow structure. Cyclomatic complexity can be calculated using a tool for control flow of cyclomatic complexity that generates a control flow graph from the source code or directly scans the source code. Cyclomatic complexity is useful for software testing and development because it helps us estimate how difficult it will be to test, debug and maintain a program, design better programs by avoiding unnecessary complexity and refactor our code when needed, and achieve better test coverage by indicating how many test cases are needed to cover all possible paths in a program. 4e3182286b