ExampleToken.sol

pragma solidity 0.4.21;

import "./Utils/SafeMath.sol";

contract ExampleToken{

    using SafeMath for uint256;

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

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


    function transfer(address _to, uint256 _value)
      public
      returns (bool success)
    {
      require(_to != address(0));
      require(_value <= balances[msg.sender]);

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

    function transferFrom
      (address _from,
        address _to,
        uint256 _value)
        public
        returns (bool success) {
      require(_to != address(0));
      require(_value <= balances[_from]);
      require(_value <= allowed[_from][msg.sender]);

      balances[_from] = balances[_from].add(_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)
      public
      onlyWhenTransferable
      returns (bool success)
    {
      allowed[msg.sender][_spender] = _value;
      Approval(msg.sender, _spender, _value);
      return true;
    }
    
    function balanceOf(address _owner) view public returns (uint256 balance) {
        return balances[_owner];
    }

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

}