Deposit And Withdraw

depositandwithdraw.sol

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

// Deposit funds into a contract and keep track of the funds
contract HelloWorld {
    mapping (address => uint) public bal;


    fallback() external payable {}

    receive() external payable {

    }

    function deposit() payable public {
        require(msg.value > 0, "I need money bro!");

        bal[msg.sender] += msg.value;
    }

    function full_withdraw() public {
        require(bal[msg.sender] > 0, "Soul, you are empty!");
        bal[msg.sender] = 0;

        payable(msg.sender).call{value: bal[msg.sender]}("");
    }

    /// @dev user can spec the amount of ether they want to withdraw
    function spec_withdraw(uint _amount) public returns (bool) {
        uint coverted_amount = _amount * 10 ** 18;

        require(bal[msg.sender] > coverted_amount, "Soul, Fund me Now!");
        bal[msg.sender] = bal[msg.sender] - coverted_amount;

        (bool sent, ) = payable(msg.sender).call{value: coverted_amount}("");

        return sent;
    }
}