Adding an owner

It's a good idea to have an owner of a contract and give them the sole right to perform admin-level actions such as the rewarding of a doer, so let's define and set an owner:

pragma solidity ^0.4.17;


contract TaskMaster {
    mapping (address => uint) public balances; // balances of everyone
    address public owner; // owner of the contract

    function TaskMaster() public {
        owner = msg.sender;        
        balances[msg.sender] = 10000;
    }
}

The owner of the contract is set to msg.sender, the address instantiating the contract. You will learn more about msg.sender and other Solidity special variables in the next chapter.