Can you explain the principle of operation of RESTful API and its main characteristics?

RESTful API is an architectural style for creating web services based on REST (Representational State Transfer) principles. Its main idea is to use standard HTTP methods to interact with resources.

Main characteristics of RESTful API:

• Resource-oriented: all data is represented as resources with unique URIs.
• Use of HTTP methods:
  • GET — retrieve a resource
  • POST — create a resource
  • PUT — update a resource
  • DELETE — delete a resource
• HTTP status codes: to inform about the result of an operation (e.g., 200 OK, 404 Not Found).
• Stateless: each request contains all necessary information; the server does not store client state.
• Support for various data formats: most commonly JSON or XML.

Example of a request to a RESTful API in C++ using the libcurl library:

#include <curl/curl.h>

int main() {
    CURL *curl = curl_easy_init();
    if(curl) {
        curl_easy_setopt(curl, CURLOPT_URL, "https://api.example.com/users/123");
        curl_easy_setopt(curl, CURLOPT_HTTPGET, 1L);
        CURLcode res = curl_easy_perform(curl);
        curl_easy_cleanup(curl);
    }
    return 0;
}

Thus, RESTful API provides a simple and standardized way for client-server interaction via HTTP.