IERC20_v1.sol

pragma solidity ^0.5.0;

contract IERC20 {
    function totalSupply() public view returns (uint256);
    function balanceOf(address _account) public view returns (uint256);
    function transfer(address _to, uint256 _tokens) public returns (bool);
    function approve(address _spender, uint256 _tokens) public returns (bool);
    function transferFrom(address _from, address _to, uint256 _tokens) public returns (bool);
    function allowance(address _account, address _spender) public view returns (uint256);

    event Transfer(address indexed _from, address indexed _to, uint256 _tokens);
    event Approval(address indexed _tokenOwner, address indexed _spender, uint256 _tokens);
}