C4 is not a coding language. Instead, C4 refers to the C4 model, a structured approach for visualizing and documenting software system architecture.
What is the C4 Model?
The C4 model, created by Simon Brown, is a lean graphical notation technique designed to depict the architecture of software systems. It provides a way to communicate software architecture at different levels of abstraction, making it easier for various audiences—from technical developers to non-technical stakeholders—to understand how a system is built and how its parts fit together.
This model is particularly useful for:
- Improving communication about the software system among team members and stakeholders.
- Onboarding new team members by providing clear architectural overviews.
- Facilitating architectural reviews and decision-making.
- Maintaining an up-to-date understanding of complex systems.
For more in-depth information, you can refer to resources like the C4 Model: Importance, Use Cases, and Examples documentation.
The Four Levels of the C4 Model
The name "C4" is an abbreviation for the four hierarchical levels of the model: Context, Container, Component, and Code. Each level provides a progressively more detailed view of the software system.
| Level | Description | Focus |
|---|---|---|
| Context | The highest level, showing the software system in its environment, how users interact with it, and how it relates to other external systems. It provides a "big picture" view. | Who uses the system? What does it integrate with? |
| Container | Zooms into the system to show the high-level building blocks or "containers" that make up the software system. These are independently deployable units (e.g., web applications, mobile apps, databases, file systems, message queues). | How is the system broken down into deployable units? |
| Component | Zooms into a single container to show the components within it. A component is a grouping of related code behind a well-defined interface (e.g., services, repositories, controllers). | What are the major logical parts within a container? |
| Code | The lowest level, showing the implementation details of a single component. This can include specific classes, interfaces, objects, and functions within the codebase. | How is a component implemented at a code level? (Often generated) |
It is at the "Code" level where actual programming language elements become visible, but the C4 model itself is an abstraction above any specific coding language. It provides a language-agnostic way to discuss system architecture.
Practical Application and Tools
Architects and development teams use the C4 model to create a set of diagrams that can be used for various purposes, from initial design discussions to ongoing maintenance. Tools like Structurizr, PlantUML, and Mermaid support the creation of C4 diagrams, allowing teams to generate and maintain these architectural views as code.
The C4 model does not dictate a specific coding language, but rather provides a framework for understanding and communicating how software systems are built, regardless of the underlying technologies used for development.
