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A Guide to Application Programming Interface (API)

  • Yamini
  • Jan 06, 2022
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About API


An Application Programming Interface, better known as API is basically a software intermediary. Its primary function is to allow two applications to communicate with each other.


Whenever we are using an app like Facebook or Instagram or even when we are looking at the weather updates on our phone as to when it's going to rain today, API comes into play.


API offers you an additional layer of security. It not only saves your phone data from being exposed to the server but also the server is never exposed to your phone. Only the data that is needed the most is shared, thus communication occurs with small packets of relevant data. (Source)


Some examples include;


Whenever we use an application, for instance, Facebook or Messenger, the application gets connected to the internet and generates data that gets transferred to a server. The data is retrieved and interpreted by the server that sends it back to your device once the required actions have been performed.


The application finally interprets the data and displays the desired information in a much readable format. This complete procedure takes place via an application programming interface.


You can consider API as a food delivery person that brings your desired food from the restaurant to your doorstep. However, API works in a bi-directional manner. 


Here is another common example, suppose you wish to book a hotel online but you cannot use the official website of the hotel you are looking for. You will use a hotel booking service such as MakeMyTrip for booking a room. The service actually interacts with the hotel's API to get the required information about availability, features, options, and add-ons, etc. 


The API takes the hotel's response to your request and delivers it back to the online hotel booking service. What you get after the entire process is updated and highly relevant information.


(Must Read: Software-Defined Networking (SDN): An Overview)



Characteristics of a Modern API 


API has completely transformed from its basic definition of being a generic connectivity interface to an application. Now, API has incorporated some characteristics that increase its significance and prominence in the world of computing technology.


Here are the four features that make APIs extraordinarily valuable and useful:


  • Standards such as HTTP and REST are adhered to by modern APIs. These are not only developer-friendly, highly accessible but also readily comprehensible to the users.


  • They are treated more like products made specifically to be consumed by specific groups of users such as mobile developers. They are documented and developed into a version such that specific audiences can get their expectations regarding the maintenance and lifestyle of APIs fulfilled in a much more efficient manner. 

  • They are not only standardized but also possess a much stronger discipline for security and governance, along with being monitored and managed for performance and scale.


  • Modern API can be aptly described as productized software. The modern API has its own software development lifecycle (SDLC) for designing, testing, building, managing, and versioning.  


The biggest advantage of modern APIs is that they are really well documented for consumption and versioning.


(Also check: Know All About Intelligent Automation)



Different types of APIs


APIs can be classified on two bases, according to Altextsoft;


First, on the basis of availability or release policies, APIs can be divided into three major categories:


1. Private APIs


These APIs are solely used within an organization. This goes without saying that these APIs are mostly developed for company employees. Common use cases are the integration of company systems or apps or the creation of entirely new systems by utilizing existing resources that are readily available.


2. Partner APIs


These APIs are openly promoted but they are only available to known business partners. The potential target audiences for such apps are business users or end customers. The popular use case for these APIs is software integration between two organizations.


3. Public, Developer-facing, or External APIs


These APIs are available for any third-party developer. Apps that utilize public APIs are mostly developed for end consumers. As this API release policy is the most accessible, it helps in boosting brand awareness and encouraging external innovation. These APIs can either be open or commercial.


  • Open APIs are absolutely free of charge. All their features are public and can be used without restrictive terms and conditions. This means that an application can be developed using this API without explicit approval from the API supplier or mandatory licensing fees. The API description and any related documentation need to be openly available, and the API can be freely used to create and test applications.
  • Commercial APIs can be used only after paying subscription fees or on a pay-as-you-go basis. Publishers usually offer free trials that enable users to evaluate an API before making a subscription purchase. Nowadays businesses are benefiting from opening their APIs for public use.


According to IBM, APIs can also be categorized on the basis of use cases i.e., systems for which they are designed.


4. Database APIs


Database APIs offer communication between an application and a database management system. Developers work with databases by writing queries to access data, change tables, etc. 


For instance, the Drupal 7 Database API enables users to write unified queries for different databases, both proprietary and open-source (Oracle, MongoDB, PostgreSQL, MySQL, CouchDB, and MSSQL). A common example is ORDS database API, which is embedded into Oracle REST Data Services.


5. Operating systems APIs


These APIs define how applications use the resources and services of operating systems. Every OS has its set of APIs, for instance, Windows API or Linux API (kernel–user-space API and kernel internal API).


Apple offers API references for macOS and iOS in its developer documentation. APIs for building applications for Apple’s macOS desktop operating system is included in the Cocoa developer tools. Those building apps for the iOS mobile operating system use Cocoa Touch, which is a modified version of Cocoa.


6. Remote APIs


Remote APIs define standards of interaction for applications running on different machines. To put it simply, one software product accesses resources located outside the device that requests them.


Since two remotely located applications are connected over a communications network or the internet, most remote APIs are written based on web standards. Two examples of remote application programming interfaces are Java Database Connectivity API and Java Remote Method Invocation API.


7. Web APIs


This is the most common API class. Web APIs provide machine-readable data and functionality transfer between web-based systems representing client-server architecture. 


These APIs basically deliver requests from web applications and responses from servers using Hypertext Transfer Protocol (HTTP). Developers use web APIs to increase the functionality of their apps or sites. For example, the Pinterest API comes with tools for adding users’ Pinterest data like boards or Pins to a website. 


Google Maps API enables the addition of a map with an organization’s location. Most businesses use more than a single API to connect applications and share information. Some require an API management tool to help them control, distribute, and analyze different APIs. 



Ending Note 


This blog ends here. While reaching the end of the blog on the application programming interface, we can clearly see that APIs hold a significant share of a business's revenue. Top companies such as Google, eBay, Salesforce.com, Amazon, and Expedia generate revenue from their APIs.


This marketplace of APIs is better known as the economy of application programming interface. APIs not only hold significance from the software development angle but also from the viewpoint of business collaboration. 


According to the Fourth State of API Integration Report of 2020, 83 percent of participants find API integration “critical” to their businesses and IT infrastructures. Decision-makers and developers need to choose the API that is well-suited for a company's requirements and can be leveraged well.

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