contract TokenERC20 {
	string public name;
	string public symbol;
	uint8 public decimals = 18;
	uint256 public totalSupply;

	// 用mapping保存每个地址对应的余额
	mapping (address => uint256) public balanceOf;
	// 存储对账号的控制
	mapping (address => mapping (address => uint256)) public allowance;
	// 事件，用来通知客户端交易发生
	event Transfer(address indexed from, address indexed to, uint256 value);
	// 事件，用来通知客户端代币被消费
	event Burn(address indexed from, uint256 value);
	
	/*
	*初始化构造
	*/
	function TokenERC20(uint256 initialSupply, string tokenName, string tokenSymbol) public {
		totalSupply = initialSupply * 10 ** uint256(decimals);  // 供应的份额，份额跟最小的代币单位有关，份额 = 币
		balanceOf[msg.sender] = totalSupply;                // 创建者拥有所有的代币
		name = tokenName;                                   // 代币名称
		symbol = tokenSymbol;                               // 代币符号
}

	//代币交易转移的内部实现
	function _transfer(address _from, address _to, uint _value) internal {
		// 确保目标地址不为0x0，因为0x0地址代表销毁
		require(_to != 0x0);
		// 检查发送者余额
		require(balanceOf[_from] >= _value);
		// 确保转移为正数个
		require(balanceOf[_to] + _value > balanceOf[_to]);
		
		// 以下用来检查交易，
		uint previousBalances = balanceOf[_from] + balanceOf[_to];
		// Subtract from the sender
		balanceOf[_from] -= _value;
		
		// Add the same to the recipient
		balanceOf[_to] += _value;
		Transfer(_from, _to, _value);
		
		// 用assert来检查代码逻辑。
		assert(balanceOf[_from] + balanceOf[_to] == previousBalances);
}

	/*****
	**代币交易转移
	**从自己（创建交易者）账号发送`_value`个代币到 `_to`账号
	**@param _to 接收者地址
	**@param _value 转移数额
	**/
	function transfer(address _to, uint256 _value) public {
		_transfer(msg.sender, _to, _value);
	 }
	 
	 /*****
	**账号之间代币交易转移
	**@param _from 发送者地址
	**@param _to 接收者地址
	**@param _value 转移数额
	**/
	function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
		require(_value <= allowance[_from][msg.sender]);     // Check allowance
		allowance[_from][msg.sender] -= _value;
		_transfer(_from, _to, _value);
		return true;
	}
	 /*****
	**设置某个地址（合约）可以创建交易者名义花费的代币数
	**允许发送者`_spender` 花费不多于 `_value` 个代币
	**@param _spender The address authorized to spend
	**@param _value the max amount they can spend
	**/
	function approve(address _spender, uint256 _value) public
		returns (bool success) {
		allowance[msg.sender][_spender] = _value;
		return true;
	}
	/*****
	**设置允许一个地址（合约）以我（创建交易者）的名义可最多花费的代币数
	**@param _spender 被授权的地址（合约）
	**@param _value 最大可花费代币数
	**@param _extraData 发送给合约的附加数据
	**/
	function approveAndCall(address _spender, uint256 _value, bytes _extraData)
	 public
	 returns (bool success) {
	 tokenRecipient spender = tokenRecipient(_spender);
	 if (approve(_spender, _value)) {
		// 通知合约
		spender.receiveApproval(msg.sender, _value, this, _extraData);
		return true;
		}
	 }
	///销毁我（创建交易者）账户中指定个代币
	function burn(uint256 _value) public returns (bool success) {
		require(balanceOf[msg.sender] >= _value);   // Check if the sender has enough
		balanceOf[msg.sender] -= _value;            // Subtract from the sender
		totalSupply -= _value;                      // Updates totalSupply
		Burn(msg.sender, _value);
		return true;
	}
	/*****
	**销毁用户账户中指定个代币
	**Remove `_value` tokens from the system irreversibly on behalf of `_from
	**@param _from the address of the sender
	**@param _value the amount of money to burn
	**/
	function burnFrom(address _from, uint256 _value) public returns (bool success) {
		require(balanceOf[_from] >= _value);                // Check if the targeted balance is enough
		require(_value <= allowance[_from][msg.sender]);    // Check allowance
		balanceOf[_from] -= _value;                         // Subtract from the targeted balance
		allowance[_from][msg.sender] -= _value;             // Subtract from the sender's allowance
		totalSupply -= _value;                              // Update totalSupply
		Burn(_from, _value);
		return true;
	}
}
function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
		require(_value <= allowance[_from][msg.sender]);     // Check allowance
		allowance[_from][msg.sender] -= _value;
		_transfer(_from, _to, _value);
		return true;
	}
/*****
 	**账号之间代币交易转移
 	**@param _from 发送者地址
 	**@param _to 接收者地址
 	**@param _value 转移数额
 	**/