what is ? in api code example

Example 1: what is an api

An application program interface (API) is a set of routines, protocols, and
tools for building software applications.

Basically, an API specifies how software components should interact.
Additionally, APIs are used when programming graphical user interface (GUI)
components.

A good API makes it easier to develop a program by providing all the
building blocks. A programmer then puts the blocks together.

Example 2: what is api

API (Application Programming Interface) helps in communication 
and data exchange between two software systems. It is the channel which 
connects two software systems communicate with one another.


An API forms the middle layer of a three-layered application pyramid, 
consisting of a data layer, a server layer and a presentation layer. 
While the data layer is concerned with data storage and the presentation 
layers are concerned with the user interface, the server layer is composed 
of business logic that defines the way for users to interact with various 
functions, features, and information. 

RESTful API ==> plain text, html, xml, json
SOAP ==> more secure, works with only xml

Example 3: what is an api

=> On a bare minimum explanation, API are function prototypes which enable the
   user to use the functionality of any component by making a function call 
   without revealing the internal workings of the component.

=> It is a mode of abstraction from the lower layers of software stack , so as 
   to only provide service when needed for higher layers.

=> An API can manifest in many forms, it can be a simple function call in C,
   it can be web service API such as Twitter or FB API, it can be a library call
   to OS kernel, or can be an interrupt routine.


=> API can be just a standalone call or in form of libraries. API are part 
   and parcel of software interaction and data transfer.

Hope this clarifies.