> For the complete documentation index, see [llms.txt](https://www.pranaypourkar.co.in/the-programmers-guide/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://www.pranaypourkar.co.in/the-programmers-guide/system-design/system-design-methodology/diagrams/uml-diagrams/plantuml/component-diagram.md).

# Component Diagram

## About

A Component Diagram represents the high-level structure of a system, showing software components, their dependencies, and interfaces. It is used to visualize module-level architecture and how components interact within a system.

{% hint style="success" %}
Refer to the official documentation for more details - <https://plantuml.com/component-diagram>
{% endhint %}

### **Key Elements**

1. **Components**
   * Represented as **rectangles with a small box** (or `<<component>>` stereotype).
   * Define **independent modules** of a system (e.g., `UserService`, `PaymentService`).
2. **Interfaces**
   * Represented as **circles** or `<<interface>>` notation.
   * Show **exposed functionalities** of components.
3. **Dependencies**
   * **Dashed arrows** indicate dependency relationships (e.g., one component depends on another).
4. **Relationships**
   * **Provided/Required Interfaces** – Shows **what a component offers or consumes**.
   * **Direct Communication** – Arrows representing **message passing**.

## 1. Banking System

This represents a **Microservices Architecture** in a banking system.

```java
@startuml
title Banking Microservices - Component Diagram

package "Banking System" {
    [User Service] --> [Auth Service] : Authenticate User
    [User Service] --> [Account Service] : Retrieve Account Details
    [Account Service] --> [Transaction Service] : Process Transactions
    [Transaction Service] --> [Notification Service] : Send Alerts
    [Transaction Service] --> [Database] : Store Transactions
}

@enduml
```

<figure><img src="https://3632859567-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FPd6ktrA5pPLsZJktj2fm%2Fuploads%2FfY9fxb3i9O4qfRAvVRo4%2Fplantuml-component-diagram-1.png?alt=media&amp;token=73f2c23a-14e1-4f84-95b3-aded1150e538" alt="" width="343"><figcaption></figcaption></figure>


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