function transfer(address _to, uint256 _value) public
  {
    
    require(transferLock == 0); 
    
    require(balanceOf[msg.sender] >= _value);
    
    require((balanceOf[_to] + _value) >= balanceOf[_to]);
    
    balanceOf[msg.sender] -= _value;
    
    balanceOf[_to] += _value;
    
    emit Transfer(msg.sender, _to, _value);
  }