The structure of a smart contract

A contract is like a class. A contract contains state variables, functions, function modifiers, events, structures, and enums. Contracts also support inheritance. Inheritance is implemented by copying code at the time of compiling. Smart contracts also support polymorphism.

Let's look at an example of a smart contract to get an idea about what it looks like:

contract Sample 
{ 
    //state variables 
    uint256 data; 
    address owner; 

    //event definition 
    event logData(uint256 dataToLog);  

    //function modifier 
    modifier onlyOwner() { 
        if (msg.sender != owner) throw; 
        _; 
    } 

    //constructor 
    function Sample(uint256 initData, address initOwner){ 
        data = initData; 
        owner = initOwner; 
    } 

    //functions 
    function getData() returns (uint256 returnedData){ 
        return data; 
    } 

    function setData(uint256 newData) onlyOwner{ 
        logData(newData); 
        data = newData; 
 ...