pragma solidity ^0.5.0;

// ----------------------------------------------------------------------------
// 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);
}

// ----------------------------------------------------------------------------
// Safe Math Library
// ----------------------------------------------------------------------------
contract SafeMath {
function safeAdd(uint a, uint b) public pure returns (uint c) {
c = a + b;
require(c >= a);
}
function safeSub(uint a, uint b) public pure returns (uint c) {
require(b <= a); c = a - b; } function safeMul(uint a, uint b) public pure returns (uint c) { c = a * b; require(a == 0 || c / a == b); } function safeDiv(uint a, uint b) public pure returns (uint c) { require(b > 0);
c = a / b;
}
}


contract GSTORE is ERC20Interface, SafeMath {
string public name;
string public symbol;
uint8 public decimals; // 18 decimals is the strongly suggested default, avoid changing it

uint256 public _totalSupply;

mapping(address => uint) balances;
mapping(address => mapping(address => uint)) allowed;

/**
* Constrctor function
*
* Initializes contract with initial supply tokens to the creator of the contract
*/
constructor() public {
name = "GSTORE";
symbol = "GSTO";
decimals = 8;
_totalSupply = 1000000000000000000;

balances[msg.sender] = _totalSupply;
emit Transfer(address(0), msg.sender, _totalSupply);
}

function totalSupply() public view returns (uint) {
return _totalSupply  - balances[address(0)];
}

function balanceOf(address tokenOwner) public view returns (uint balance) {
return balances[tokenOwner];
}

function allowance(address tokenOwner, address spender) public view returns (uint remaining) {
return allowed[tokenOwner][spender];
}

function approve(address spender, uint tokens) public returns (bool success) {
allowed[msg.sender][spender] = tokens;
emit Approval(msg.sender, spender, tokens);
return true;
}

function transfer(address to, uint tokens) public returns (bool success) {
balances[msg.sender] = safeSub(balances[msg.sender], tokens);
balances[to] = safeAdd(balances[to], tokens);
emit Transfer(msg.sender, to, tokens);
return true;
}

function transferFrom(address from, address to, uint tokens) public returns (bool success) {
balances[from] = safeSub(balances[from], tokens);
allowed[from][msg.sender] = safeSub(allowed[from][msg.sender], tokens);
balances[to] = safeAdd(balances[to], tokens);
emit Transfer(from, to, tokens);
return true;
}
}