API Definition

The API definition stands for Application Programming Interface. It’s the connection point that allows you to connect your program to a set of tools and resources in another software system. This interface enables software developers to create software applications that are compatible with a particular OS. APIs also help to connect applications with backend systems or other software libraries and frameworks. In all of the above cases, API acts as the intermediate interface that facilitates this process.

APIs can be categorized into these types based on their usage.

• Operating System API
  When you create a software application you can send a request to the OS to use its tools and resources such as access to hardware resources or file systems through your application.
• Web API
  The APIs that can be accessed using the HTTP protocol is called the web APIs. When you want to access a service or resource belonging to a backend system such as retrieving, saving, and updating existing data in the database through a front end application over the HTTP protocol, you can send a request using a Web API. Web APIs are usually created using JavaScript Object Notation ( JSON ) format.
• Library /Framework
  Library or framework APIs are used within a single software system when you want to access certain services or resources of another software library or a framework in your program. The use of these APIs can vary based on the programming language you use.