What are APIs and where can I find them?

Many people have heard the term API. It is used in the context of application development andsites, often appears in programmer memes. So what is an API? Where is it used, where to find it, and what are its benefits for business? Let's try to figure it out.

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What does API mean?

API— an abbreviation ofApplication Programming InterfaceLiterally, it translates asapplication programming interface.However, definitions are also usedapplication programming interface or application programming interface. 

In practice, an API is a set of components that allow one computer program (a bot or a website) to use another. In other words, it's a mechanism that allows two software components to interact with each other using a set of definitions and protocols.

An API can also be considered an intermediary between programs that defines the rules of "communication." That's why the term "interface"—the boundary between objects—is used in its name. One program doesn't care how another program works. Developers simply use the interface: they send a request and receive a response.

An API builds “bridges” that allow one program to access another program’s data (or specific functionality).

According to the established definition, an API is represented by a set of functions. There may be one or more of these.

The World Wide Web and Remote Servers

To understand how APIs are used in development and how they benefit businesses, it's important to understand how the World Wide Web (WWW) works.

The World Wide Web is a vast network of interconnected web servers located around the world.

A web server is a computer program that runs on a network-connected computing device and uses the HTTP protocol to transfer data.

A regular laptop or PC can be turned into a server, and it can host a website. When creating websites, before they're launched to the general public, developers use local servers.

How do APIs work?

All internet users interact with APIs without even realizing it. For example, when sending images or...

By opening any internet page, the user interacts with the API of a remote server.

The API is a part of the server that performs two important tasks:

1. receives requests;
2. sends responses.

API architecture is typically explained using the terms "client" and "server." The "client" is the application sending the request, and the "server" is the application sending the response.

API as a finished product

Many companies offer APIs as ready-made products. For example, Weather Underground sells access to its API for retrieving weather data.

• Let's say you want to create your own weather forecast app.
• Without using the API, your app would have to open weather.com the same way a human would (by typing the address of the site they're looking for into the browser's address bar).
• Thanks to the API, the app will quickly send a request to weather.com, load the received data into its interface, and the user will instantly see weather information on their smartphone screen.

In this example, the "server" refers to the Weather Underground database, and your mobile app is the "client."

Another example of the API in action.

A user purchases something online and pays with a card. Here's how it works:

• he provides card details and clicks the “Continue” button;
• the site (or application) “tells” whether the entered data is correct;
• If everything is correct, the purchase payment transaction is carried out.

Many processes in the system that must send this response to the buyer occur in the background:

• the website (or application) sends the user's card data to the remote application;
• it verifies the information received;
• and produces the result, sending it back.

This is how REST APIs (a type of API architecture) work. Clients and servers exchange data via the HTTP protocol. The key feature is that data transfer is stateless. This means that servers do not store client data between user requests.

API for applications

For example, if you want to create an iOS app, you don't need to develop the OS from scratch: Apple offers a large API base. Planning to set up fingerprint authentication on Android (for example, the My Kyivstar app offers this option)? There are APIs for that. And there are thousands of such examples.

The API speeds up and simplifies work, and sometimes it even feels like magic. The simplest example of "magic" is translating posts on Instagram or Twitter. We simply click the "Translate" button, and in two seconds we can read the text. And yet, we have no idea how many tasks and processes were performed to get this translation.

API for websites

APIs are used in web development. They typically contain a specific set of HTTP requests, as well as a definition of the structure of HTTP responses, expressed using XML or JSON format.

In website building, the principle of using APIs works the same as with applications. For a website to function, you don't need to, for example, create a custom browser or write code for it.

Most modern websites use at least several third-party APIs. And many tasks already have ready-made solutions prepared by third-party developers. It's often easier, faster, and more reliable to use a ready-made library, service, etc.

API types

APIs are classified both by architecture and by scope of application.

Classification by architecture

SOAP API— a simple object access protocol. The client and server exchange messages via XML. But SOAP is a protocol of the past—more flexible ones already exist.

RPC APIare a remote procedure call system: the client executes a function (or procedure) on the server, and the server sends the result back to the client.

REST API— highly flexible APIs. The client sends requests to the server as data, the server uses this client input to run internal functions and returns output back to the client (we discussed this above using the online payment example).

Websocket API— a modern web API development that uses JSON objects to transfer data. WebSocket APIs support two-way communication between client applications and the server. The server can send callback messages to connected clients, making it even more efficient than popular REST APIs.

Classification by scope of application

Private APIs— internal APIs of organizations, which are used only to connect systems and data within the business.

Public APIscan be used by anyone. Such client-facing APIs (they are made open to end users) become a product in themselves.

Partner APIsare available only to authorized third-party developers to facilitate partnerships between businesses.

Composite APIscombine two or more different APIs to solve complex system requirements or behavior.

Where to find the API?

There are dedicated marketplaces that bring together API buyers and sellers. Platforms like RapidAPI, APILayer, and many others allow API providers (developers or enterprises) to showcase and promote their APIs, and buyers (other developers) can browse and purchase these offerings.

API marketplace platforms help developers:

• find potential clients and expand your target audience reach;
• gain knowledge and improve your products;
• sell them without any problems and increase your income.

Consumers have the opportunity to find successful APIs by ratings, statistics, and tables, get the necessary information on forums, and check API reviews with the help of other developers to choose a high-quality API.

API Courses

1. On courseThe React Developer Course with Hooks, Context API and Redux They teach you how to create applications using the JavaScript library React and many other skills.
2. Program Developing APIs with Google Cloud's Apigee API Platform includes three courses that teach API development using the Apigee API platform.
3. Well API Testing Trainingaims to teach API testing using DLLs, Frameworks, and WebAPI testing using GUI extensions.
4. Rest API Automation With Rest Assured— a course for studying Rest API automation frameworks.
5. Well REST API Design, Development & Managementoffers current practices for developing RESTful APIs.
6. Linkedin learning has a whole section with a list of courses on API testing -Learn API Testing.

Conclusion

APIs, by facilitating interaction between programs, simplify the programming process when creating applications and websites. Many companies develop APIs for clients or for internal use. This helps develop business processes and increase profits.

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