pragma solidity ^0.4.21;

interface IERC20 {
    function totalSupply() constant returns (uint256 totalSupply);
    function balanceOf(address _owner) constant returns (uint256 balance);
    function transfer(address _to, uint256 _value) returns (bool success);
    function transferFrom(address _from, address _to, uint256 _value) returns (bool success);
    function approve(address _spender, uint256 _value) returns (bool success);
    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);
}


/**
 * @title SafeMath
 * @dev Math operations with safety checks that throw on error
 */
library SafeMath {

  /**
  * @dev Multiplies two numbers, throws on overflow.
  */
  function mul(uint256 a, uint256 b) internal pure returns (uint256) {
    if (a == 0) {
      return 0;
    }
    uint256 c = a * b;
    assert(c / a == b);
    return c;
  }

  /**
  * @dev Integer division of two numbers, truncating the quotient.
  */
  function div(uint256 a, uint256 b) internal pure returns (uint256) {
    // assert(b > 0); // Solidity automatically throws 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 Substracts two numbers, throws on overflow (i.e. if subtrahend is greater than minuend).
  */
  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    assert(b <= a);
    return a - b;
  }

  /**
  * @dev Adds two numbers, throws on overflow.
  */
  function add(uint256 a, uint256 b) internal pure returns (uint256) {
    uint256 c = a + b;
    assert(c >= a);
    return c;
  }
}

contract DSC is IERC20 {

    // ---- DSC Specifications ----
    // Name: DSC (Data Science Coin)
    // Total Supply: 10 billion
    // Initial Ownership Ratio: 100%
    // Another(separate) CONTRACT to be created in the future for crowdsale(ICO)
    //  
    // DSC Phases
    // 1. Create DSC (tokens)
    // 2. Individually distribute tokens to existing BigPlace users & notify them
    // 3. Private Sale
    // 4. Crowdsale (ICO)
    // 5. PROMOTE DATA SCIENCE !
    // 
    // **This is the second try. 
    //-----------------------------
    
    using SafeMath for uint256;
    
    uint256 public constant _totalSupply = 10000000000000000000000000000;
    
    string public constant symbol = "DSC";
    string public constant name = "Data Science Coin";
    uint8 public constant decimals = 18;
    
    mapping(address => uint256) balances;
    mapping(address => mapping(address => uint256)) allowed;
    
    function DSC() {
        balances[msg.sender] = 10000000000000000000000000000;
    }
    
    function totalSupply() constant returns (uint256 totalSupply) {
        return _totalSupply;
    }
    
    function balanceOf(address _owner) constant returns (uint256 balance) {
        return balances[_owner];
    }
    
    function transfer(address _to, uint256 _value) returns (bool success) {
        require(
            balances[msg.sender] >= _value
            && _value > 0
        );
        balances[msg.sender] = balances[msg.sender].sub(_value);
        balances[_to] = balances[_to].add(_value);
        Transfer(msg.sender, _to, _value);
        return true;
    }
    
    function transferFrom(address _from, address _to, uint256 _value) returns (bool success) {
        require(
            allowed[_from][msg.sender] >= _value
            && balances[_from] >= _value
            && _value > 0
        );
        balances[_from] = balances[_from].sub(_value);
        balances[_to] = balances[_to].sub(_value);
        allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
        Transfer(_from, _to, _value);
        return true;
    }
    
    function approve(address _spender, uint256 _value) returns (bool success) {
        allowed[msg.sender][_spender] = _value;
        Approval(msg.sender, _spender, _value);
        return true;
    }
    
    function allowance(address _owner, address _spender) constant returns (uint256 remaining){
        return allowed[_owner][_spender];
    }
    
    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);

}