Representational State Transfer (REST) is an architectural style that defines a set of constraints to be used for creating web services. REST API (also known as RESTful API) is a way of accessing web services in a simple and flexible way without having any processing. It provides a set of constraints and principles for creating scalable, stateless, and interoperable systems. RESTful APIs (Application Programming Interfaces) adhere to these principles, making them easy to consume and integrate with other systems. Here are the key characteristics and an example of a RESTful API:

Characteristics of a RESTful API:

1. Stateless: The server does not store any client context between requests. Each request contains all the necessary information to be understood and processed by the server. 2. Client-Server: The client and server are separate entities that communicate over the network. They are independent and can evolve separately, allowing for better scalability and flexibility. 3. Uniform Interface: The API follows a uniform set of constraints, which include standard HTTP methods (GET, POST, PUT, DELETE) and well-defined resource representations (usually in JSON or XML). 4. Resource-Based: Resources are identified by unique URLs (Uniform Resource Locators). Each resource has its own URL, and the API interacts with these resources using HTTP methods. 5. Hypermedia as the Engine of Application State (HATEOAS): The API includes hypermedia links within the responses, allowing clients to navigate the application state dynamically. Example of a RESTful API: Consider an example of a simple RESTful API for managing books. It provides endpoints for retrieving, creating, updating, and deleting books. 1. Retrieve all books:

GET /api/books

2. Retrieve a specific book:

GET /api/books/{id}

3. Create a new book:

POST /api/books
Request Body: { "title": "The Alchemist", "author": "Paulo Coelho" }

4. Update an existing book:

PUT /api/books/{id}
Request Body: { "title": "The Alchemist", "author": "Paulo Coelho", "year": 1988 }

5. Delete a book:

DELETE /api/books/{id}

In this example, each book is represented as a resource identified by its unique ID. The API follows the HTTP methods to perform various operations on the books. The client can interact with the API by making requests to the appropriate endpoints. The RESTful nature of the API is reflected in the use of standard HTTP methods and URLs to interact with resources. The API provides a uniform interface for clients to manipulate book resources and follows the stateless constraint by not relying on client context between requests. It's important to note that while this example demonstrates the basic principles of a RESTful API, the design and implementation of RESTful APIs can vary depending on the specific requirements of the system and the API design guidelines.