contract ERC20Token { mapping(address => uint256) public balances; function setSomeonesBalance(address owner, uint256 amount) public { balances[owner] = amount; } function transferTokensBetweenAddresses(address sender, address receiver, uint256 amount) public { balances[sender] -= amount; // deduct/debit the sender's balance balances[receiver] += amount; // credit the reciever's balance } }