contract Token{
uint256 public totalSupply;
function balanceOf(address _owner) public constant returns (uint256 balance);
function transfer(address _to, uint256 _value) public returns (bool success);
function transferFrom(address _from, address _to, uint256 _value) public returns (bool success);
//消息发送账户设置账户_spender能从发送账户中转出数量为_value的token
function approve(address _spender, uint256 _value) public returns (bool success);
function allowance(address _owner, address _spender) public constant returns (uint256 remaining);
//发生转账时必须要触发的事件
event Transfer(address indexed _from, address indexed _to, uint256 _value);
//当函数approve(address _spender, uint256 _value)成功执行时必须触发的事件
event Approval(address indexed _owner, address indexed _spender, uint256
_value);
}
function approve(address _spender, uint256 _value) public returns (bool success);

//消息发送账户设置账户_spender能从发送账户中转出数量为_value的token