Token.sol

/*
This contract is intended for educational purposes, you are fully responsible
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Most, basic default, standardised Token contract. No "pre-mine". Tokens need to be created by a derived contract (e.g. crowdsale)

Original taken from https://github.com/ConsenSys/Tokens/blob/master/Token_Contracts/contracts/Standard_Token.sol
which is based on standardised APIs: https://github.com/ethereum/wiki/wiki/Standardized_Contract_APIs
*/

/// @title Standard Token Contract.

contract TokenInterface {

    mapping (address => uint256) balances;
    mapping (address => mapping (address => uint256)) allowed;

	/// @return total amount of tokens
    uint256 public totalSupply;

    /// @param _owner The address from which the balance will be retrieved
    /// @return The balance
    function balanceOf(address _owner) constant returns (uint256 balance);

    /// @notice send `_value` tokens to `_to` from `msg.sender`
    /// @param _to The address of the recipient
    /// @param _value The amount of tokens to be transfered
    /// @return Whether the transfer was successful or not
    function transfer(address _to, uint256 _value) returns (bool success);

    /// @notice send `_value` tokens to `_to` from `_from` on the condition it is approved by `_from`
    /// @param _from The address of the sender
    /// @param _to The address of the recipient
    /// @param _value The amount of tokens to be transfered
    /// @return Whether the transfer was successful or not
    function transferFrom(address _from, address _to, uint256 _value) returns (bool success);

    /// @notice `msg.sender` approves `_spender` to spend `_value` tokens on its behalf
    /// @param _spender The address of the account able to transfer the tokens
    /// @param _value The amount of tokens to be approved for transfer
    /// @return Whether the approval was successful or not
    function approve(address _spender, uint256 _value) returns (bool success);

    /// @param _owner The address of the account owning tokens
    /// @param _spender The address of the account able to transfer the tokens
    /// @return Amount of remaining tokens of _owner that _spender is allowed to spend
    function allowance(address _owner, address _spender) constant returns (uint256 remaining);

    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);
}

contract Token is TokenInterface {

    function transfer(address _to, uint256 _value) returns (bool success) {
        return transferFrom(msg.sender, _to, _value);
    }

    function transferFrom(address _from, address _to, uint256 _value) returns (bool success) {
        if (balances[_from] >= _value && (_from == msg.sender || allowed[_from][msg.sender] >= _value) && _value > 0) {
            balances[_to] += _value;
            balances[_from] -= _value;
            if (_from != msg.sender)
                allowed[_from][msg.sender] -= _value;
            Transfer(_from, _to, _value);
            return true;
        }
        else
            return false;
    }

    function approve(address _spender, uint256 _value) returns (bool success) {
        allowed[msg.sender][_spender] = _value;
        Approval(msg.sender, _spender, _value);
        return true;
    }

    function balanceOf(address _owner) constant returns (uint256 balance) {
        return balances[_owner];
    }

    function allowance(address _owner, address _spender) constant returns (uint256 remaining) {
      return allowed[_owner][_spender];
    }
}