blog

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What is an API?

API = Application Programming Interface

An API is a set of rules that allows two software systems to talk to each other.

It acts as a bridge or contract between:

• a client (who wants something)
• a server (who provides it)

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Example

Imagine a weather app:

• You open app → it needs weather data
• It sends request to weather API
• API returns:

{
  "city": "Bangalore",
  "temp": "28°C",
  "condition": "Cloudy"
}

You never see how weather is calculated—you just get the result.

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Why APIs exist?

APIs help systems:

• communicate easily
• hide internal complexity
• reuse functionality
• connect different apps

Example:

• Google Maps API → used by Uber, Zomato, Ola

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API Styles List

API Styles
├─ REST
├─ RPC
├─ GraphQL
└─ SOAP

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1. REST (Most common)

simple web rules

• Uses URLs like:

  GET /users
  POST /orders
  

• Uses HTTP methods: GET, POST, PUT, DELETE
• Easy and widely used

Example:

GET /weather/bangalore

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2. RPC (Remote Procedure Call)

calling a function on another computer

• You call methods directly:

  getWeather("Bangalore")
  

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3. GraphQL

ask exactly what you want

Instead of getting fixed data, you request fields:

{
  user {
    name
    email
  }
}

Advantage: no extra/unwanted data

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4. SOAP

old, strict, formal system

• Uses XML
• Very structured
• Used in banking, enterprise systems

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