What exactly is the meaning of an API? [closed]

Answer 1

Lets say you are developing a game and you want the game user to login their facebook profile(to get your profile information) before playing it,so how your game is going to access facebook? Now here comes the API.Facebook has already written the program(API) for you to do it, you have to just use those programs in your game application.using Facebook-API you can use their services in your application.Here is a good and detailed look on API... http://money.howstuffworks.com/business-communications/how-to-leverage-an-api-for-conferencing1.htm

Answer 2

An API is a set of commands, functions, and protocols which programmers can use when building software for a specific OS or any other software. The API allows programmers to use predefined functions to interact with the operating system, instead of writing them from scratch. All computer operating systems, such as Windows, Unix, and the Mac OS and language such as Java provide an application program interface for programmers.

Source

Answer 3

Searches should include Wikipedia, which is surprisingly good for a number of programming concepts/terms such as Application Programming Interface:

What is an API?

An application programming interface (API) is a particular set of rules ('code') and specifications that software programs can follow to communicate with each other. It serves as an interface between different software programs and facilitates their interaction, similar to the way the user interface facilitates interaction between humans and computers.

How is it used?

The same way any set of rules are used.

When and where is it used?

Depends upon realm and API, naturally. Consider these:

1. The x86 (IA-32) Instruction Set (very useful ;-)
2. A BIOS interrupt call
3. OpenGL which is often exposed as a C library
4. Core Windows system calls: WinAPI
5. The Classes and Methods in Ruby's core library
6. The Document Object Model exposed by browsers to JavaScript
7. Web services, such as those provided by Facebook's Graph API
8. An implementation of a protocol such as JNI in Java

Happy coding.

Answer 4

Well, in addition to all the answers, I am just adding an example.

As others said API stands for Application Programming Interface through which softwares can interact with each other. Note, not a human interaction.

Where it is used

An example: You are buying an item online through your credit card. You will provide credit card details and press 'continue' button. It will tell you whether your information is correct or not. To provide these results, there are lot of things in the background.

The application will send your credit card details to a remote application which will validate your information and send the result back to your application. API is used in this scenario.

I hope it helps for the beginners who don't understand really what API is.

ANOTHER EXAMPLE

Weather application

Without API - Weather application must open weather.com site and read the details as a human does.

With API - Weather application will send a message to weather.com and receive the result and then display it.

SOURCE - Various online resources

Answer 5

Application program interface (API) is a set of routines, protocols, and tools for building software applications. An API specifies how software components should interact and 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.

source: http://www.webopedia.com/TERM/A/API.html

Answer 6

In layman's terms, I've always said an API is like a translator between two people who speak different languages. In software, data can be consumed or distributed using an API (or translator) so that two different kinds of software can communicate. Good software has a strong translator (API) that follows rules and protocols for security and data cleanliness.

I"m a Marketer, not a coder. This all might not be quite right, but it's what I"ve tried to express for about 10 years now...