Hello world code for solidity, a programming language to deploy smart contract to ethereum platform. Online IDE can be found here: http://remix.ethereum.org/

hodor.sol

pragma solidity ^0.4.0;

/*
Simple contract that returns a greeting
*/

contract Hodor {
    address creator;
    string greeting;
    
    function Hodor(string _greeting) {
        greeting = _greeting;
        creator = msg.sender;
    }
    
    // returns the current greeting
    function greet() constant returns (string) {
        return greeting;        
    }
    
    // changes the current greeting
    function setGreeting(string _greeting) {
        greeting = _greeting;
    }    
}