/**
 *Submitted for verification at Etherscan.io on 2019-08-19
*/

pragma solidity >=0.4.22 <0.6.0;

    // ----------------------------------------------------------------------------
    // Safe maths
    // ----------------------------------------------------------------------------
    library SafeMath {
        function add(uint a, uint b) internal pure returns (uint c) {
            c = a + b;
            require(c >= a);
        }
        function sub(uint a, uint b) internal pure returns (uint c) {
            require(b <= a);
            c = a - b;
        }
        function mul(uint a, uint b) internal pure returns (uint c) {
            c = a * b;
            require(a == 0 || c / a == b);
        }
        function div(uint a, uint b) internal pure returns (uint c) {
            require(b > 0);
            c = a / b;
        }
    }

    // ----------------------------------------------------------------------------
    // ERC Token Standard #20 Interface
    // ----------------------------------------------------------------------------
    contract ERC20Interface {
        function totalSupply() public view returns (uint);
        function balanceOf(address tokenOwner) public view returns (uint balance);
        function allowance(address tokenOwner, address spender) public view returns (uint remaining);
        function transfer(address to, uint tokens) public returns (bool success);
        function approve(address spender, uint tokens) public returns (bool success);
        function transferFrom(address from, address to, uint tokens) public returns (bool success);

        event Transfer(address indexed from, address indexed to, uint tokens);
        event Approval(address indexed tokenOwner, address indexed spender, uint tokens);
    }

    // ----------------------------------------------------------------------------
    // Bimin Token Contract
    // ----------------------------------------------------------------------------
    contract FOS is ERC20Interface{
        using SafeMath for uint;
        
        string public symbol;
        string public name;
        uint8 public decimals;
        uint _totalSupply;
        mapping(address => uint) balances;
        mapping(address => mapping(address => uint)) allowed;

        // ------------------------------------------------------------------------
        // Constructor
        // ------------------------------------------------------------------------
        constructor(address _owner) public{
            symbol = "FOS";
            name = "Future Of Service";
            decimals = 18;
            _totalSupply = 1000000000; //10,000,000,000
            balances[_owner] = totalSupply();
            emit Transfer(address(0),_owner,totalSupply());
        }

        function totalSupply() public view returns (uint){
        return _totalSupply * 10**uint(decimals);
        }

        // ------------------------------------------------------------------------
        // Get the token balance for account `tokenOwner`
        // ------------------------------------------------------------------------
        function balanceOf(address tokenOwner) public view returns (uint balance) {
            return balances[tokenOwner];
        }

        // ------------------------------------------------------------------------
        // Transfer the balance from token owner's account to `to` account
        // - Owner's account must have sufficient balance to transfer
        // - 0 value transfers are allowed
        // ------------------------------------------------------------------------
        function transfer(address to, uint tokens) public returns (bool success) {
            // prevent transfer to 0x0, use burn instead
            require(to != address(0));
            require(balances[msg.sender] >= tokens );
            require(balances[to] + tokens >= balances[to]);
            balances[msg.sender] = balances[msg.sender].sub(tokens);
            balances[to] = balances[to].add(tokens);
            emit Transfer(msg.sender,to,tokens);
            return true;
        }
        
        // ------------------------------------------------------------------------
        // Token owner can approve for `spender` to transferFrom(...) `tokens`
        // from the token owner's account
        // ------------------------------------------------------------------------
        function approve(address spender, uint tokens) public returns (bool success){
            allowed[msg.sender][spender] = tokens;
            emit Approval(msg.sender,spender,tokens);
            return true;
        }

        // ------------------------------------------------------------------------
        // Transfer `tokens` from the `from` account to the `to` account
        // 
        // The calling account must already have sufficient tokens approve(...)
        // for spending from the `from` account and
        // - From account must have sufficient balance to transfer
        // - Spender must have sufficient allowance to transfer
        // - 0 value transfers are allowed
        // ------------------------------------------------------------------------
        function transferFrom(address from, address to, uint tokens) public returns (bool success){
            require(tokens <= allowed[from][msg.sender]); //check allowance
            require(balances[from] >= tokens);
            balances[from] = balances[from].sub(tokens);
            balances[to] = balances[to].add(tokens);
            allowed[from][msg.sender] = allowed[from][msg.sender].sub(tokens);
            emit Transfer(from,to,tokens);
            return true;
        }
        // ------------------------------------------------------------------------
        // Returns the amount of tokens approved by the owner that can be
        // transferred to the spender's account
        // ------------------------------------------------------------------------
        function allowance(address tokenOwner, address spender) public view returns (uint remaining) {
            return allowed[tokenOwner][spender];
        }
    }