Visualizing Software Architecture: A Guide to the C4 Model

Clarify Your Software Architecture with the C4 Architecture Model

In software development, a strong architecture is crucial for building dependable and adaptable systems. In most cases, however, there is a lack of a cohesive documentation process for these complicated software structures. Many organizations don’t have documentation. Those few organizations that do have documentation save them on a mix of Miro, FigJam, or LucidChart. Some places even take pictures of drawings on whiteboards and save them somewhere.

Enter the C4 architecture model: a simple yet powerful approach that simplifies and organizes software systems into a simple way.

The C4 model (Context, Containers, Components, and Code) is a hierarchical approach to documenting software architecture. It mainly uses these three icons to describe each entity in the application.

Each “C” in C4 is a software architecture diagram in various levels of detail. The diagrams of each “C” are as follows:

Context

These are the highest-level diagrams that show the scope of the entire system and how users and other external systems interact with it. Its primary audience is all the stakeholders interested in the system.

The diagram in a C4 software architecture for an Internet Bank System looks something like the following:

Containers

The next level of the C4 architecture is containers, which can be found by “zooming in” to one of the main systems of interest. Each container encapsulates a collection of related applications and their dependencies, providing a clear boundary between different components of the system.

Components

Within each container, you’ll find components — the building blocks that make up the container’s functionality. Components are typically libraries, packages, or modules that encapsulate specific functionalities or data.

For instance, if you decompose the API Application container in our Internet Banking System it might look like this:

Code

The last level of the C4 architecture is “Code”. This level is mainly composed of UML class diagrams about the model. For example, if we decompose the Account Summary Controller to be something like this:

The C4 architecture model provides a practical approach to software architecture documentation and communication. It empowers teams to navigate and document complex software systems with confidence using documentation rules that are easy to learn.

By offering a hierarchical framework for visualizing system architecture at different levels of detail, and by using simple icons to describe each component, the C4 model also makes any architecture easy to understand.

Whether you’re starting a new project or aiming to improve the architecture of an existing system, consider adopting the C4 model as a valuable tool in your architectural toolkit.