I have written and complied a smart contract written in Solidity for token and crowdsale. Compilation was successful with no errors in Remix IDE. Here is my smart contract

pragma solidity ^0.4.25;

library SafeMath {

    * @dev Multiplies two numbers, reverts on overflow.
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
    // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
    // benefit is lost if 'b' is also tested.
    // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
        if (a == 0) {
            return 0;

        uint256 c = a * b;
        require(c / a == b);
        return c;

    * @dev Integer division of two numbers truncating the quotient, reverts on division by zero.
    function div(uint256 a, uint256 b) internal pure returns (uint256) {

        require(b > 0); // Solidity only automatically asserts when dividing by 0
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;

    * @dev Subtracts two numbers, reverts on overflow (i.e. if subtrahend is greater than minuend).
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {

        require(b <= a);
        uint256 c = a - b;

        return c;

    * @dev Adds two numbers, reverts on overflow.
    function add(uint256 a, uint256 b) internal pure returns (uint256) {

        uint256 c = a + b;
        require(c >= a);

        return c;

    * @dev Divides two numbers and returns the remainder (unsigned integer modulo),
    * reverts when dividing by zero.
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {

        require(b != 0);
        return a % b;

interface ERC20 {

    function balanceOf(address who) external view returns (uint256);
    function transferToken(address to, uint256 value) external returns (bool);
    // function allowance(address owner, address spender) external view returns (uint256);
    // function transferFrom(address from, address to, uint256 value) external returns (bool);
    // function approve(address spender, uint256 value) external returns (bool);
    event Transfer(address indexed from, address indexed to, uint256 value);
    event TransferEther(address indexed who,uint256 value);
    // event Approval(address indexed owner, address indexed spender, uint256 value);


contract Owned {

    address internal owner;

    address internal operator;

    function transferOwnership(address newOwner) public returns(bool success);

    function setOperator(address newoperator) public returns(bool success);

    function FreezeICO() public returns(bool success);

    function setRate(uint8 newRate) public returns(bool success);

    function addToWhitelist(address who) public returns(bool success);

    event Ownership_Transferred(address indexed previousOwner, address indexed newOwner);

    event Freeze_Ico(bool success);

    event change_Rate(uint8 newRate);

    event change_Operator(address operator);

    event Added_to_whitelist(bool success);

    constructor(address newoperator) public{

         owner = msg.sender;
         operator = newoperator;


    modifier onlyOwner {

        require(msg.sender == owner);



    modifier onlyOperator {

        require(msg.sender == operator);



contract SafeToken is ERC20,Owned {

    using SafeMath for uint;

    string public _name = "DOHA";
    string public _symbol = "DO";
    uint8 public _decimals = 18;
    uint256 public _totalSupply;
    uint8 public _rate;
    uint256 public _deadline;
    uint256 public _icoCompleted;
    bool public _freeze;

    mapping (address => uint256) public balances;
    mapping (address => mapping (address => uint256)) public allowed;
    mapping (address => bool) public whiteList;

    constructor(uint256 totalSupply, uint8 rate,  uint duration) public {

        _totalSupply = totalSupply * 10**uint(_decimals);
        _deadline = now + duration * 1 minutes;
        balances[msg.sender] = _totalSupply;
        _icoCompleted = 0;
        _freeze = false;


    function name()public view returns (string) {
        return _name;

    function symbol()public view returns (string) {
        return _symbol;

    function deadline()public view returns (uint) {
        return _deadline;

    function totalSupply()public view returns (uint) {
        return _totalSupply;

    function currentOwner() public view returns (address) {
        return owner;

    function icoStatus() public view returns (uint) {
        return _icoCompleted;

    function freezeStatus() public view returns (bool) {
        return _freeze;

    function white_List(address who) public view returns (bool) {

        return whiteList[who];

    modifier icoFunctioning {

        require(_freeze == false);
        require(_icoCompleted < _totalSupply);

    modifier deadlineCheck {

        require(now <= _deadline);

    modifier whiteListed(address who) {


    function() external payable icoFunctioning deadlineCheck whiteListed(msg.sender){


        uint _tokens;
        _tokens = SafeMath.mul(msg.value,_rate);

        require(_tokens <= balances[owner]);

        balances[owner] = SafeMath.sub(balances[owner],_tokens);
        balances[msg.sender] = SafeMath.add(balances[msg.sender],_tokens);
        _icoCompleted = SafeMath.add(_icoCompleted,_tokens);

        emit TransferEther(msg.sender,_tokens);


    function FreezeICO() public onlyOwner returns(bool success) {

        _freeze = !_freeze;
        emit Freeze_Ico(_freeze);
        return _freeze;

    function addToWhitelist(address who) public onlyOperator deadlineCheck returns(bool success){

        whiteList[who] =true;
        emit Added_to_whitelist(whiteList[who]);


    function balanceOf(address who) external view returns (uint256 balance) {

        return balances[who];

   function transferToken(address _to, uint256 _value) external returns (bool) {

         require(_to != address(0));
         require(_value <= balances[msg.sender]);

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

    function setRate(uint8 newRate) public onlyOwner icoFunctioning returns (bool success) {

        require(newRate != _rate);

        _rate = newRate;
        emit change_Rate(_rate); 
        return true;


    function transferOwnership(address newOwner) public onlyOwner returns(bool success) {

        require(newOwner != address(0));
        balances[newOwner] = balances[owner];
        balances[owner] = 0;
        emit Ownership_Transferred(owner, newOwner);
        owner = newOwner;
        return true;


    function setOperator(address newoperator) onlyOwner deadlineCheck public returns(bool success){

        require(newoperator != address(0));

        emit change_Operator(operator);
        return true;



When deploying I got a message like this enter image description here

I don't have much experience in Ethereum. Need help


I found what's wrong here, your contract Owned { has a parameterised constructor but you are using it as a default constructor here :

contract SafeToken is ERC20,Owned {

while inheriting it's properties.

Hence the error that you are not implementing all the functions!


Either you need to remove the parameterised constructor and it's initialization like this:

constructor() public { // observe that the parameters are removed

     owner = msg.sender;
     // operator = newoperator; // comment or remove this line



You can add parameter while inheriting like this:

contract SafeToken is ERC20, Owned(msg.sender) { // NOTE: You can add any address

Choice is yours. Cheers!


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