advance-erc20-at-course.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;

contract XXXToken {
    string public name;
    string public symbol;
    uint256 public totalSupply;
    mapping(address => uint256) private balances;
    address owner;

    event Transfer(address _from, address _to, uint256 _value);

    constructor(string memory _name, string memory _symbol, uint256 _totalSupply) {
        name = _name;
        symbol = _symbol;
        totalSupply = _totalSupply;
        owner = msg.sender;
        balances[msg.sender] = _totalSupply;
    }

    function transfer(address _to, uint256 _amount) public {
        require(balances[msg.sender] >= _amount, "You don't have enough balance!");
        balances[msg.sender] = balances[msg.sender] - _amount;
        balances[_to] = balances[_to] + _amount;

        emit Transfer(msg.sender, _to, _amount);
    }
    
    function balanceOf(address account) public view returns(uint256) {
        return balances[account];
    }
}