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;
...