pragma solidity ^0.4.16;

contract owned {
    address public owner;

    function owned() public {
        owner = msg.sender;
    }

    modifier onlyOwner {
        require(msg.sender == owner);
        _;
    }

    function transferOwnership(address newOwner) onlyOwner public {
        owner = newOwner;
    }
}

interface tokenRecipient { function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData) external; }

contract TokenERC20 {
    // Public variables of the token
    string public name;
    string public symbol;
    uint8 public decimals = 18;
    // 18 decimals is the strongly suggested default, avoid changing it
    uint256 public totalSupply;

    // This creates an array with all balances
    mapping (address => uint256) public balanceOf;
    mapping (address => mapping (address => uint256)) public allowance;

    // This generates a public event on the blockchain that will notify clients
    event Transfer(address indexed from, address indexed to, uint256 value);

    // This notifies clients about the amount burnt
    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 {
        // Prevent transfer to 0x0 address. Use burn() instead
        require(_to != 0x0);
        // Check if the sender has enough
        require(balanceOf[_from] >= _value);
        // Check for overflows
        require(balanceOf[_to] + _value > balanceOf[_to]);
        // Save this for an assertion in the future
        uint previousBalances = balanceOf[_from] + balanceOf[_to];
        // Subtract from the sender
        balanceOf[_from] -= _value;
        // Add the same to the recipient
        balanceOf[_to] += _value;
        emit Transfer(_from, _to, _value);
        // Asserts are used to use static analysis to find bugs in your code. They should never fail
        assert(balanceOf[_from] + balanceOf[_to] == previousBalances);
    }

    function transfer(address _to, uint256 _value) public returns (bool success) {
        _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;
        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;               
        emit 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;                  
        emit Burn(_from, _value);
        return true;
    }
}

contract USC is owned, TokenERC20 {
    mapping (address => bool) public frozenAccount;
    event FrozenFunds(address target, bool frozen);
    function USC(
        uint256 initialSupply,
        string tokenName,
        string tokenSymbol
    ) TokenERC20(initialSupply, tokenName, tokenSymbol) public {}

    function _transfer(address _from, address _to, uint _value) internal {
        require (_to != 0x0);                               // Prevent transfer to 0x0 address. Use burn() instead
        require (balanceOf[_from] >= _value);               // Check if the sender has enough
        require (balanceOf[_to] + _value >= balanceOf[_to]); // Check for overflows
        require(!frozenAccount[_from]);                     // Check if sender is frozen
        require(!frozenAccount[_to]);                       // Check if recipient is frozen
        balanceOf[_from] -= _value;                         // Subtract from the sender
        balanceOf[_to] += _value;                           // Add the same to the recipient
        emit Transfer(_from, _to, _value);
    }

    function mintToken(address target, uint256 mintedAmount) onlyOwner public {
        balanceOf[target] += mintedAmount;
        totalSupply += mintedAmount;
        emit Transfer(0, this, mintedAmount);
        emit Transfer(this, target, mintedAmount);
    }

    function freezeAccount(address target, bool freeze) onlyOwner public {
        frozenAccount[target] = freeze;
        emit FrozenFunds(target, freeze);
    }

}