contract ERC20CompatibleToken is owned, IERC20 {
    using SafeMath for uint;
    
    // Public variables of the token
    string public name;
    string public symbol;
    uint8 public decimals = 18;
    uint256 public totalSupply;
    
    mapping(address => uint) balances; // List of user balances.
    
    event Transfer(address indexed from, address indexed to, uint value);
    event Approval(address indexed owner, address indexed spender, uint256 value);
    mapping (address => mapping (address => uint256)) internal allowed;
    mapping (address => bool) public frozenAccount;
    
    /**
    * Constrctor function
    *
    * Initializes contract with initial supply tokens to the creator of the contract
    */
    constructor(
      uint256 initialSupply,
      string memory tokenName,
      string memory tokenSymbol, 
      address owner
    ) public {
        totalSupply = initialSupply * 10 ** uint256(decimals);  // Update total supply with the decimal amount
        balances[owner] = totalSupply;                    // Give the creator all initial tokens
        name = tokenName;                                       // Set the name for display purposes
        symbol = tokenSymbol;                                   // Set the symbol for display purposes
    }
  
    function totalSupply() public view returns (uint256) {
            return totalSupply;
        }
      
    /**
     * @dev Returns balance of the `_owner`.
     *
     * @param _owner   The address whose balance will be returned.
     * @return balance Balance of the `_owner`.
     */
    function balanceOf(address _owner) public constant returns (uint balance) {
        return balances[_owner];
    }
    
    
    /**
     * @dev Transfer the specified amount of tokens to the specified address.
     *
     * @param _to    Receiver address.
     * @param _value Amount of tokens that will be transferred.
     */
    function transfer(address _to, uint _value) public {
        require(!frozenAccount[msg.sender]);                    // Check if sender is frozen
        require(!frozenAccount[_to]);                           // Check if recipient is frozen

        balances[msg.sender] = balances[msg.sender].sub(_value);
        balances[_to] = balances[_to].add(_value);
        
        emit Transfer(msg.sender, _to, _value);
        return ;
    }


   
  
  
    /**
    * @dev Function to check the amount of tokens that an owner allowed to a spender.
    * @param _owner address The address which owns the funds.
    * @param _spender address The address which will spend the funds.
    * @return A uint256 specifying the amount of tokens still available for the spender.
    */
    function allowance(address _owner, address _spender) public view returns (uint256) {
        return allowed[_owner][_spender];
    }

    /**
    * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
    *
    * @param _spender The address which will spend the funds.
    * @param _value The amount of tokens to be spent.
    */
    function approve(address _spender, uint256 _value) public returns (bool) {
        allowed[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }

    /**
    * @dev Transfer tokens from one address to another
    * @param _from address The address which you want to send tokens from
    * @param _to address The address which you want to transfer to
    * @param _value uint256 the amount of tokens to be transferred
    */
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
        
        require(_value <= balances[_from]);
        require(_value <= allowed[_from][msg.sender]);
    
        require(!frozenAccount[_from]);                         // Check if sender is frozen
        require(!frozenAccount[_to]);                           // Check if recipient is frozen
        
        balances[_from] = balances[_from].sub(_value);
        balances[_to] = balances[_to].add(_value);
        allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
        
        emit Transfer(_from, _to, _value);
        return true;
    }

    /**
    * approve should be called when allowed[_spender] == 0. To increment
    * allowed value is better to use this function to avoid 2 calls (and wait until
    * the first transaction is mined)
    * From MonolithDAO Token.sol
    */
    function increaseApproval(address _spender, uint _addedValue) public returns (bool) {
        allowed[msg.sender][_spender] = allowed[msg.sender][_spender].add(_addedValue);
        emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
        return true;
    }
    
    function decreaseApproval(address _spender, uint _subtractedValue) public returns (bool) {
        uint oldValue = allowed[msg.sender][_spender];
        if (_subtractedValue > oldValue) {
            allowed[msg.sender][_spender] = 0;
        } else {
            allowed[msg.sender][_spender] = oldValue.sub(_subtractedValue);
        }
        emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
        return true;
    }
    
    /* This generates a public event on the blockchain that will notify clients */
    event FrozenFunds(address target, bool frozen);
    
    /// @notice `freeze? Prevent | Allow` `target` from sending & receiving tokens
    /// @param target Address to be frozen
    /// @param freeze either to freeze it or not
    function freezeAccount(address target, bool freeze) onlyOwner public {
        frozenAccount[target] = freeze;
        emit FrozenFunds(target, freeze);
    }

}
function balanceOf(address _owner) public constant returns (uint balance) {
    return balances[_owner];
}

/**
 * @dev Returns balance of the `_owner`.
 *
 * @param _owner   The address whose balance will be returned.
 * @return balance Balance of the `_owner`.
 */