pragma solidity ^0.4.16;

 
interface tokenRecipient { function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData) public; }

 
contract TokenERC20 {

string public name;

string public symbol;

uint8 public decimals = 18; // 18 是建议的默认值

uint256 public totalSupply;

 
mapping (address => uint256) public balanceOf; //

mapping (address => mapping (address => uint256)) public allowance;

 
event Transfer(address indexed from, address indexed to, uint256 value);

event Approval(address indexed owner, address indexed spender, uint256 value);

event Burn(address indexed from, uint256 value);

 
 
function TokenERC20(uint256 initialSupply, string tokenName, string tokenSymbol) public {

totalSupply = initialSupply * 10 ** uint256(decimals);

balanceOf[msg.sender] = totalSupply;

name = tokenName;

symbol = tokenSymbol;

}

 
 
function _transfer(address _from, address _to, uint _value) internal {

require(_to != 0x0);

require(balanceOf[_from] >= _value);

require(balanceOf[_to] + _value > balanceOf[_to]);

uint previousBalances = balanceOf[_from] + balanceOf[_to];

balanceOf[_from] -= _value;

balanceOf[_to] += _value;

Transfer(_from, _to, _value);

assert(balanceOf[_from] + balanceOf[_to] == previousBalances);

}

 
function transfer(address _to, uint256 _value) public returns (bool) {

_transfer(msg.sender, _to, _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;

}

 
function approve(address _spender, uint256 _value) public

returns (bool success) {

allowance[msg.sender][_spender] = _value;

Approval(msg.sender, _spender, _value);

return true;

}

 
function approveAndCall(address _spender, uint256 _value, bytes _extraData) public returns (bool success) {

tokenRecipient spender = tokenRecipient(_spender);

if (approve(_spender, _value)) {

spender.receiveApproval(msg.sender, _value, this, _extraData);

return true;

}

}

 
function burn(uint256 _value) public returns (bool success) {

require(balanceOf[msg.sender] >= _value);

balanceOf[msg.sender] -= _value;

totalSupply -= _value;

Burn(msg.sender, _value);

return true;

}

 
function burnFrom(address _from, uint256 _value) public returns (bool success) {

require(balanceOf[_from] >= _value);

require(_value <= allowance[_from][msg.sender]);

balanceOf[_from] -= _value;

allowance[_from][msg.sender] -= _value;

totalSupply -= _value;

Burn(_from, _value);

return true;

}

}