Generally speaking, an API, or Application Programming Interface, is a set of programming instructions that tell web-based software applications how to interact and communicate with each other, or with other words, it is software code that comes along a web application and is designed for computer consumption rather than a direct user interaction, and that grants access to the application’s services which developers could integrate into their own web products.
While APIs were first used in the 1960s with procedural languages and typically delivered as libraries, the term is first recorded in use, in the field of database systems, in a conference paper, titled: The Relational and Network Approaches: Comparison of the Application Programming Interfaces and presented at the 1974 ACM SIGFIDET (now SIGMOD) workshop on Data description, access and control in Amsterdam, The Netherlands.
In the 80s and 90s object-oriented programming (OOP) emerged along the building of cross organizational apps with XML over HTTP. In 1998, the SOAP (Simple Object Access Protocol) was designed as a standard messaging protocol used by web services to exchange data, to become notorious for its complexity to build and use. As an alternative, the REST (Representative State Transfer) architecture style was first presented in Roy Fielding’s 2000 dissertation on software architecture to set the rules for a common language through which software could communicate.
The birth of web APIs preceded the introduction of Fielding’s concept with a few months, when on February 7, 2000 Salesforce became the first provider to launch publicly available XML APIs to enable customers to share data across different business applications and deliver what we know today as Software-as-a-Service.
On November 20, 2000, eBay launched its API, along with the eBay Developers Program to “provide the tools that developers need to create applications based on eBay technology.” Amazon stepped into the world of e-commerce driven APIs, launching its Amazon Web Services and allowing developers to incorporate Amazon’s content and characteristics into their web products.
The birth of social platforms led the way to new APIs based on social sharing features and building of connections.
On June 29th, 2006, Google launched Google Maps API to start a trend of API mashups, mashing together data from different Web applications to make a new one; like a map showing all restaurants nearby or tracking a hiking route.
Amazon’s EC2 or Elastic Compute Cloud storage services and Google’s App Engine paved the way for cloud computing platforms for developers and virtual servers for hosting web applications.
The real milestone came in June 2009 with Apple’s iPhone 3G release and the App Store allowing owners to download applications – the start of the era of mobile apps where APIs are the driving force.