An API is a set of programming code that enables data transmission between one software product and another. It also contains the terms of this data exchange.
Application programming interfaces (API) consist of two components:
1. Technical specification describing the data exchange options between solutions with the specification done in the form of a request for processing and data delivery protocols.
2. Software interface written to the specification that represents it.
The software that needs to access information or functionality from another software, calls its API while specifying the requirements of how data/functionality must be provided. The other software returns data/functionality requested by the former application.
And the interface by which these two applications communicate is what the API specifies.
APIs are sometimes considered contracts, where documentation is an agreement between the parties: “If party first sends a remote request structured a particular way, this is how the second party’s software will respond.”
Each API contains and is implemented by function calls – language statements that request software to perform particular actions and services. Function calls are phrases composed of verbs and nouns, for example:
- Start or finish a session
- Get amenities for a single room type
- Restore or retrieve objects from a server.
APIs serve numerous purposes. Generally, they can simplify and speed up software development. Developers can add functionality from other providers to existing solutions or build new applications using services by third-party providers. In all these cases, specialists don’t have to deal with source code, trying to understand how the other solution works. They simply connect their software to another one. In other words, APIs serve as an abstraction layer between two systems, hiding the complexity and working details of the latter.
Types of APIs
Below are the types of APIs commonly used.
1. Private API
Private APIs are designed for improving solutions and services within an organization. In-house developers or contractors may use these APIs to integrate a company’s IT systems or applications, build new systems or customer-facing apps leveraging existing systems. Even if apps are publicly available, the interface itself remains available only for those working directly with the API publisher. The private strategy allows a company to fully control the API usage.
2. Partner API
Partner APIs are openly promoted but shared with business partners who have signed an agreement with the publisher. The common use case for partner APIs is software integration between two parties. A company that grants partners with access to data or capability benefits from extra revenue streams. At the same time, it can monitor how the exposed digital assets are used, ensure whether third-party solutions using their APIs provide decent user experience, and maintain corporate identity in their apps.
3. Public API
Public APIs are available for any third-party developers. A public API program allows for increasing brand awareness and receiving an additional source of income when properly executed.
Example of API
A popular API example is the function that enables people to log in to websites by using their Facebook, Twitter, or Google profile login details. This convenient feature allows any website to leverage an API from one of the more popular services to quickly authenticate the user, saving them the time and hassle of setting up a new profile for every website service or new membership.