// SPDX-License-Identifier: MIT

pragma solidity 0.8.1;

/**
	 * @dev Interface of the ERC20 standard as defined in the EIP.
	 */
	interface IERC20 {
	    /**
	     * @dev Returns the amount of tokens in existence.
	     */
	    function totalSupply() external view returns (uint256);
	
	    /**
	     * @dev Returns the amount of tokens owned by `account`.
	     */
	    function balanceOf(address account) external view returns (uint256);
	
	    /**
	     * @dev Moves `amount` tokens from the caller's account to `recipient`.
	     *
	     * Returns a boolean value indicating whether the operation succeeded.
	     *
	     * Emits a {Transfer} event.
	     */
	    function transfer(address recipient, uint256 amount) external returns (bool);
	
	    /**
	     * @dev Returns the remaining number of tokens that `spender` will be
	     * allowed to spend on behalf of `owner` through {transferFrom}. This is
	     * zero by default.
	     *
	     * This value changes when {approve} or {transferFrom} are called.
	     */
	    function allowance(address owner, address spender) external view returns (uint256);
	
	    /**
	     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
	     *
	     * Returns a boolean value indicating whether the operation succeeded.
	     *
	     * IMPORTANT: Beware that changing an allowance with this method brings the risk
	     * that someone may use both the old and the new allowance by unfortunate
	     * transaction ordering. One possible solution to mitigate this race
	     * condition is to first reduce the spender's allowance to 0 and set the
	     * desired value afterwards:
	     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
	     *
	     * Emits an {Approval} event.
	     */
	    function approve(address spender, uint256 amount) external returns (bool);
	
	    /**
	     * @dev Moves `amount` tokens from `sender` to `recipient` using the
	     * allowance mechanism. `amount` is then deducted from the caller's
	     * allowance.
	     *
	     * Returns a boolean value indicating whether the operation succeeded.
	     *
	     * Emits a {Transfer} event.
	     */
	    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
	
	    /**
	     * @dev Emitted when `value` tokens are moved from one account (`from`) to
	     * another (`to`).
	     *
	     * Note that `value` may be zero.
	     */
	    event Transfer(address indexed from, address indexed to, uint256 value);
	
	    /**
	     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
	     * a call to {approve}. `value` is the new allowance.
	     */
	    event Approval(address indexed owner, address indexed spender, uint256 value);
	}
	
	/*
	 * @dev Provides information about the current execution context, including the
	 * sender of the transaction and its data. While these are generally available
	 * via msg.sender and msg.data, they should not be accessed in such a direct
	 * manner, since when dealing with GSN meta-transactions the account sending and
	 * paying for execution may not be the actual sender (as far as an application
	 * is concerned).
	 *
	 * This contract is only required for intermediate, library-like contracts.
	 */
	abstract contract Context {
	    function _msgSender() internal view virtual returns (address) {
	        return msg.sender;
	    }
	
	    function _msgData() internal view virtual returns (bytes calldata) {
	        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
	        return msg.data;
	    }
	}
	
	
	/**
	 * @dev Implementation of the {IERC20} interface.
	 *
	 * This implementation is agnostic to the way tokens are created. This means
	 * that a supply mechanism has to be added in a derived contract using {_mint}.
	 * For a generic mechanism see {ERC20PresetMinterPauser}.
	 *
	 * TIP: For a detailed writeup see our guide
	 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
	 * to implement supply mechanisms].
	 *
	 * We have followed general OpenZeppelin guidelines: functions revert instead
	 * of returning `false` on failure. This behavior is nonetheless conventional
	 * and does not conflict with the expectations of ERC20 applications.
	 *
	 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
	 * This allows applications to reconstruct the allowance for all accounts just
	 * by listening to said events. Other implementations of the EIP may not emit
	 * these events, as it isn't required by the specification.
	 *
	 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
	 * functions have been added to mitigate the well-known issues around setting
	 * allowances. See {IERC20-approve}.
	 */
	contract ERC20 is Context, IERC20 {
	    mapping (address => uint256) private _balances;
	
	    mapping (address => mapping (address => uint256)) private _allowances;
	
	    uint256 private _totalSupply;
	
	    string private _name;
	    string private _symbol;
	
	    /**
	     * @dev Sets the values for {name} and {symbol}.
	     *
	     * The defaut value of {decimals} is 18. To select a different value for
	     * {decimals} you should overload it.
	     *
	     * All three of these values are immutable: they can only be set once during
	     * construction.
	     */
	    constructor (string memory name_, string memory symbol_) {
	        _name = name_;
	        _symbol = symbol_;
	    }
	
	    /**
	     * @dev Returns the name of the token.
	     */
	    function name() public view virtual returns (string memory) {
	        return _name;
	    }
	
	    /**
	     * @dev Returns the symbol of the token, usually a shorter version of the
	     * name.
	     */
	    function symbol() public view virtual returns (string memory) {
	        return _symbol;
	    }
	
	    /**
	     * @dev Returns the number of decimals used to get its user representation.
	     * For example, if `decimals` equals `2`, a balance of `505` tokens should
	     * be displayed to a user as `5,05` (`505 / 10 ** 2`).
	     *
	     * Tokens usually opt for a value of 18, imitating the relationship between
	     * Ether and Wei. This is the value {ERC20} uses, unless this function is
	     * overloaded;
	     *
	     * NOTE: This information is only used for _display_ purposes: it in
	     * no way affects any of the arithmetic of the contract, including
	     * {IERC20-balanceOf} and {IERC20-transfer}.
	     */
	    function decimals() public view virtual returns (uint8) {
	        return 18;
	    }
	
	    /**
	     * @dev See {IERC20-totalSupply}.
	     */
	    function totalSupply() public view virtual override returns (uint256) {
	        return _totalSupply;
	    }
	
	    /**
	     * @dev See {IERC20-balanceOf}.
	     */
	    function balanceOf(address account) public view virtual override returns (uint256) {
	        return _balances[account];
	    }
	
	    /**
	     * @dev See {IERC20-transfer}.
	     *
	     * Requirements:
	     *
	     * - `recipient` cannot be the zero address.
	     * - the caller must have a balance of at least `amount`.
	     */
	    function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
	        _transfer(_msgSender(), recipient, amount);
	        return true;
	    }
	
	    /**
	     * @dev See {IERC20-allowance}.
	     */
	    function allowance(address owner, address spender) public view virtual override returns (uint256) {
	        return _allowances[owner][spender];
	    }
	
	    /**
	     * @dev See {IERC20-approve}.
	     *
	     * Requirements:
	     *
	     * - `spender` cannot be the zero address.
	     */
	    function approve(address spender, uint256 amount) public virtual override returns (bool) {
	        _approve(_msgSender(), spender, amount);
	        return true;
	    }
	
	    /**
	     * @dev See {IERC20-transferFrom}.
	     *
	     * Emits an {Approval} event indicating the updated allowance. This is not
	     * required by the EIP. See the note at the beginning of {ERC20}.
	     *
	     * Requirements:
	     *
	     * - `sender` and `recipient` cannot be the zero address.
	     * - `sender` must have a balance of at least `amount`.
	     * - the caller must have allowance for ``sender``'s tokens of at least
	     * `amount`.
	     */
	    function transferFrom(address sender, address recipient, uint256 amount) public virtual override returns (bool) {
	        _transfer(sender, recipient, amount);
	
	        uint256 currentAllowance = _allowances[sender][_msgSender()];
	        require(currentAllowance >= amount, "ERC20: transfer amount exceeds allowance");
	        _approve(sender, _msgSender(), currentAllowance - amount);
	
	        return true;
	    }
	
	    /**
	     * @dev Atomically increases the allowance granted to `spender` by the caller.
	     *
	     * This is an alternative to {approve} that can be used as a mitigation for
	     * problems described in {IERC20-approve}.
	     *
	     * Emits an {Approval} event indicating the updated allowance.
	     *
	     * Requirements:
	     *
	     * - `spender` cannot be the zero address.
	     */
	    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
	        _approve(_msgSender(), spender, _allowances[_msgSender()][spender] + addedValue);
	        return true;
	    }
	
	    /**
	     * @dev Atomically decreases the allowance granted to `spender` by the caller.
	     *
	     * This is an alternative to {approve} that can be used as a mitigation for
	     * problems described in {IERC20-approve}.
	     *
	     * Emits an {Approval} event indicating the updated allowance.
	     *
	     * Requirements:
	     *
	     * - `spender` cannot be the zero address.
	     * - `spender` must have allowance for the caller of at least
	     * `subtractedValue`.
	     */
	    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
	        uint256 currentAllowance = _allowances[_msgSender()][spender];
	        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
	        _approve(_msgSender(), spender, currentAllowance - subtractedValue);
	
	        return true;
	    }
	
	    /**
	     * @dev Moves tokens `amount` from `sender` to `recipient`.
	     *
	     * This is internal function is equivalent to {transfer}, and can be used to
	     * e.g. implement automatic token fees, slashing mechanisms, etc.
	     *
	     * Emits a {Transfer} event.
	     *
	     * Requirements:
	     *
	     * - `sender` cannot be the zero address.
	     * - `recipient` cannot be the zero address.
	     * - `sender` must have a balance of at least `amount`.
	     */
	    function _transfer(address sender, address recipient, uint256 amount) internal virtual {
	        require(sender != address(0), "ERC20: transfer from the zero address");
	        require(recipient != address(0), "ERC20: transfer to the zero address");
	
	        _beforeTokenTransfer(sender, recipient, amount);
	
	        uint256 senderBalance = _balances[sender];
	        require(senderBalance >= amount, "ERC20: transfer amount exceeds balance");
	        _balances[sender] = senderBalance - amount;
	        _balances[recipient] += amount;
	
	        emit Transfer(sender, recipient, amount);
	    }
	
	    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
	     * the total supply.
	     *
	     * Emits a {Transfer} event with `from` set to the zero address.
	     *
	     * Requirements:
	     *
	     * - `to` cannot be the zero address.
	     */
	    function _mint(address account, uint256 amount) internal virtual {
	        require(account != address(0), "ERC20: mint to the zero address");
	
	        _beforeTokenTransfer(address(0), account, amount);
	
	        _totalSupply += amount;
	        _balances[account] += amount;
	        emit Transfer(address(0), account, amount);
	    }
	
	    /**
	     * @dev Destroys `amount` tokens from `account`, reducing the
	     * total supply.
	     *
	     * Emits a {Transfer} event with `to` set to the zero address.
	     *
	     * Requirements:
	     *
	     * - `account` cannot be the zero address.
	     * - `account` must have at least `amount` tokens.
	     */
	    function _burn(address account, uint256 amount) internal virtual {
	        require(account != address(0), "ERC20: burn from the zero address");
	
	        _beforeTokenTransfer(account, address(0), amount);
	
	        uint256 accountBalance = _balances[account];
	        require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
	        _balances[account] = accountBalance - amount;
	        _totalSupply -= amount;
	
	        emit Transfer(account, address(0), amount);
	    }
	
	    /**
	     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
	     *
	     * This internal function is equivalent to `approve`, and can be used to
	     * e.g. set automatic allowances for certain subsystems, etc.
	     *
	     * Emits an {Approval} event.
	     *
	     * Requirements:
	     *
	     * - `owner` cannot be the zero address.
	     * - `spender` cannot be the zero address.
	     */
	    function _approve(address owner, address spender, uint256 amount) internal virtual {
	        require(owner != address(0), "ERC20: approve from the zero address");
	        require(spender != address(0), "ERC20: approve to the zero address");
	
	        _allowances[owner][spender] = amount;
	        emit Approval(owner, spender, amount);
	    }
	
	    /**
	     * @dev Hook that is called before any transfer of tokens. This includes
	     * minting and burning.
	     *
	     * Calling conditions:
	     *
	     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
	     * will be to transferred to `to`.
	     * - when `from` is zero, `amount` tokens will be minted for `to`.
	     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
	     * - `from` and `to` are never both zero.
	     *
	     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
	     */
	    function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual { }
	}
	
	/**
	 * @dev Extension of {ERC20} that allows token holders to destroy both their own
	 * tokens and those that they have an allowance for, in a way that can be
	 * recognized off-chain (via event analysis).
	 */
	abstract contract ERC20Burnable is Context, ERC20 {
	    /**
	     * @dev Destroys `amount` tokens from the caller.
	     *
	     * See {ERC20-_burn}.
	     */
	    function burn(uint256 amount) public virtual {
	        _burn(_msgSender(), amount);
	    }
	
	    /**
	     * @dev Destroys `amount` tokens from `account`, deducting from the caller's
	     * allowance.
	     *
	     * See {ERC20-_burn} and {ERC20-allowance}.
	     *
	     * Requirements:
	     *
	     * - the caller must have allowance for ``accounts``'s tokens of at least
	     * `amount`.
	     */
	    function burnFrom(address account, uint256 amount) public virtual {
	        uint256 currentAllowance = allowance(account, _msgSender());
	        require(currentAllowance >= amount, "ERC20: burn amount exceeds allowance");
	        _approve(account, _msgSender(), currentAllowance - amount);
	        _burn(account, amount);
	    }
	}
	
	contract XTblockToken is ERC20Burnable {
	    
	    string constant public symbolString = "XTT-e20";
        string constant public nameString = "ERC20 XTblock Token";

        uint256 INITIAL_SUPPLY = 350000000;
    
       
	    constructor() ERC20(nameString, symbolString) {
		    _mint(msg.sender, INITIAL_SUPPLY * (10 ** uint256(decimals())));
		  
        }
      
    }