erc20-balanceOf.sol

contract MyERCToken {
  // Create a table so that we can map addresses
  // to the balances associated with them
  mapping(address => uint256) balances;
  // Owner of this contract
  address public owner;
  
  function balanceOf(address _owner) constant returns (uint256 balance) {
    // Return the balance for the specific address
    return balances[_owner];
  }
}