contrato basico de tokens em solidity

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

contract tokenCR {

    string _name = "token CR";
    string _symbol = "sith";
    uint8 _decimals = 8;
    uint _totalsupply ;
    mapping (address => uint) _balances ; 
    mapping (address => mapping (address => uint )) _allowance;

    event Transfer (address indexed _from , address indexed _to , uint256 _value);
    event approval (address indexed _owner , address indexed _spender , uint256 _value);

    constructor (){
        _totalsupply = 100_000 * 10 ** _decimals ;
        _balances [msg.sender] = _totalsupply ; 
    }
    function name () public view returns ( string memory){
        return _name ;
    }

    function symbol () public view returns (string memory){
        return _symbol ;
    }

    function decimals () public view returns (uint8){
        return _decimals;
    }

    function totalsupply () public view returns (uint){
        return _totalsupply ;       
    }

    function balanceOf (address _owner) public view returns (uint){
        return  _balances[_owner];
    }
 
    function transfer (address _to , uint _value ) public returns (bool){
        require(_balances [msg.sender] >= _value, "saldo insuficiente");
        _balances [msg.sender] = _balances [msg.sender] - _value ;
        _balances [_to] = _balances [_to] + _value ;
        
        emit Transfer(msg.sender, _to, _value);

        return true ;
    }

    function tranferfrom (address _from , address _to , uint value ) public returns (bool){

        require(_balances [_from] >= value , "saldo insuficiente");

        require(allowance(_from , msg.sender) >= value , unicode"sem autorizaçao");

        _balances [_from] = _balances [_from] - value ;
        _balances [_to] = _balances [_to] + value ; 

        _allowance [_from][msg.sender] = _allowance [_from][msg.sender] - value ;

        emit Transfer(_from, _to, value);

        return true;
    }

    function allowance (address _owner , address _spender) public view returns (uint){
        return _allowance [_owner][_spender];
    }

   function approve (address _spender , uint _value) public returns (bool){
       _allowance [ msg.sender][_spender] = _value ;

       emit approval(msg.sender, _spender, _value);
       return true ;
   }

}