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Token.sol

pragma solidity >=0.6.0 <0.8.0;
// SPDX-License-Identifier: MIT"
contract Token {
    mapping (address => uint256) private _balances;
    uint256 private _totalSupply;
    string private _name;
    string private _symbol;
    uint256 private _decimals;
    uint256 private theTotalSupply;
    
    constructor(string memory name, string memory symbol) public {
        // _name = "Test";
        // _symbol = "TEST";
        // _decimals = 18;
        // _totalSupply = 0;
        
        // Assign temporal variables to contract variables
        // https://docs.soliditylang.org/en/v0.5.3/contracts.html
        _name = name;
        _symbol = symbol;
        
        // You can assign the total number of token in circulation here
        // Solidity does not have decimal values so they are represented in integers
        // The standard is to repredent balances in wei units
        // https://eth-converter.com/
        _totalSupply = 1000e18; // = 1000 tokens in wei units (18 decimals)
        
        // Add balance to msg.sender, the Ethereum account that deployed the contract
        _balances[msg.sender] = 1000e18;
        
        // The ERC20 tokens have 18 decimals
        _decimals = 18;
    }
    
    /**
     * @dev Returns the name of the token
     */
    function name() public view returns (string memory) {
        return _name;
    }
    
    /**
     * @dev Set the name of the token
     */
    function setName(string memory name) public {
        _name = name;
    }
    /**
     * 
     * @dev Returns the symbol of the token
     */
     
     
    // function symbol() public view returns (string) {
    // You need to add the keyword `memory` to temporal strings
    function symbol() public view returns (string memory) {
        return _symbol;
    }
    
    /**
     * @dev Returns the decimals of the token
     */
    
    // function decimals() public view returns (uint8) {
    // The returned value does not match `_decimals` data type since it's of type uint256
    // and you are trying to return a uint8 
    function decimals() public view returns (uint256) {
        return _decimals;
    }
    
    /**
     * @dev Returns the total supply of the token
     */
    function totalSupply() public view returns (uint256) {
        // This function should return the totalSupply or amount of tokens in circulation
        // so you don't need to assign anything
        // theTotalSupply = _totalSupply;
        return theTotalSupply;
    }
    
    /**
     * @dev Returns the balance of the token
     */
    function balanceOf(address _owner) public view returns (uint256) {
        // You are missing an `s`
        // return balance[_owner];
        return _balances[_owner];
    }
    
    /**
     * @dev Returns the transfer of the token
     */
    function transfer(address _to, uint256 _value) public returns (bool success) {
        _balances[msg.sender] -= _value;
        _balances[_to] += _value;
        
        // This is not necessary or maybe you are trying to emit an Event
        // https://docs.soliditylang.org/en/v0.6.7/contracts.html#events
        // transfer(msg.sender, _to, _value); //
        
        emit Transfer(msg.sender, _to, _value);
        return true;   
    }
    
    // Declare event
    event Transfer(address sender, address recipient, uint256 amount);
}