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.deps...github...OpenZeppelin...openzeppelin-contracts...contracts...access...Ownable.sol

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "../utils/Context.sol";

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _setOwner(_msgSender());
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _setOwner(address(0));
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _setOwner(newOwner);
    }

    function _setOwner(address newOwner) private {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

.deps...github...OpenZeppelin...openzeppelin-contracts...contracts...utils...Context.sol

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @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 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) {
        return msg.data;
    }
}

.deps...github...OpenZeppelin...openzeppelin-contracts...contracts...utils...math...SafeMath.sol

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

// CAUTION
// This version of SafeMath should only be used with Solidity 0.8 or later,
// because it relies on the compiler's built in overflow checks.

/**
 * @dev Wrappers over Solidity's arithmetic operations.
 *
 * NOTE: `SafeMath` is no longer needed starting with Solidity 0.8. The compiler
 * now has built in overflow checking.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            uint256 c = a + b;
            if (c < a) return (false, 0);
            return (true, c);
        }
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b > a) return (false, 0);
            return (true, a - b);
        }
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
            // benefit is lost if 'b' is also tested.
            // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
            if (a == 0) return (true, 0);
            uint256 c = a * b;
            if (c / a != b) return (false, 0);
            return (true, c);
        }
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b == 0) return (false, 0);
            return (true, a / b);
        }
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b == 0) return (false, 0);
            return (true, a % b);
        }
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        return a + b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return a - b;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        return a * b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator.
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b <= a, errorMessage);
            return a - b;
        }
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b > 0, errorMessage);
            return a / b;
        }
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b > 0, errorMessage);
            return a % b;
        }
    }
}

demo...library.sol

pragma solidity ^0.8.0;

    import "https://github.com/OpenZeppelin/openzeppelin-contracts/contracts/utils/math/SafeMath.sol";

contract demo{
    
    using SafeMath for uint;
    
    mapping(address=>uint) tokenBalance;
    
    constructor() {
        tokenBalance[msg.sender] = 1;
    }
    
    function sendToken(address _to, uint _numberOF) public{
            tokenBalance[_to] = SafeMath.add(tokenBalance[_to],_numberOF);
            tokenBalance[msg.sender] = tokenBalance[msg.sender].sub(_numberOF,"edfeggdc");
    }
    
    function seeTokens(address _address) public view returns(uint){
        return tokenBalance[_address];
    }
    
}

demo...sol6.sol

pragma solidity ^0.6.0;

contract A{
    function D() public virtual returns(string memory){
        string memory _A = "from A";
        return _A;
    }
}

contract B{
    function D() public virtual returns(string memory){
       
    }
}

contract C is A,B{
    
    function D() public override(B, A) returns(string memory){
        string memory _C = "from C";
        return _C;
        super.D();
        
    }
}

demo...sol7.sol

pragma solidity ^0.8.3;

contract sol7{
    mapping(address=>uint) token;
   
    
    function see(uint _num) public view returns(uint){
        uint a = 2**256 -1;
        uint b;
        unchecked{
        b =    a + _num;
            
        }
        return b;
    }
}

demo.sol

pragma solidity ^0.8.0;

    import "https://github.com/OpenZeppelin/openzeppelin-contracts/contracts/utils/math/SafeMath.sol";

contract demo{
    
    using SafeMath for uint;
    
    mapping(address=>uint) tokenBalance;
    
    constructor() {
        tokenBalance[msg.sender] = 1;
    }
    
    function sendToken(address _to, uint _numberOF) public{
            tokenBalance[_to] = SafeMath.add(tokenBalance[_to],_numberOF);
            tokenBalance[msg.sender] = tokenBalance[msg.sender].sub(_numberOF,"edfeggdc");
    }
    
    function seeTokens(address _address) public view returns(uint){
        return tokenBalance[_address];
    }
    
}

Shared Wallet...Allowance.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/access/Ownable.sol";


contract Allowance is Ownable{
    
    event AllowanceAdd(address _forwho, address _fromwhome, uint _oldamount, uint _newamount);
    event AllowanceReduce(address _forwho, address _fromwhom, uint _oldamount, uint _newamount);
    
    mapping(address=>uint) public allowance;
    
    function addAllowance(address _who, uint _amount) public onlyOwner{
        emit AllowanceAdd(_who, msg.sender, allowance[_who], _amount);
        allowance[_who] = _amount;
    }
    
    function reduceAllowance(address _who, uint _amount) internal{
        emit AllowanceReduce(_who, msg.sender, allowance[_who],allowance[_who] - _amount);
        allowance[_who] -= _amount;
    }
    
    modifier ownerOrallowanceChecker(uint _amount){
        require(owner() == msg.sender || allowance[msg.sender] >= _amount, "Allowance is failed");
        _;
    }
}

Shared Wallet...SimpleWallet.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "./Allowance.sol";

contract SimpleWallet is Allowance{
 
    event WithdrawMoney(address _who, uint _amount);
    event MoneyReceived(address _who,uint _amount);
 
    fallback() external{
        
    }   
    
    receive() external payable{
        emit MoneyReceived(msg.sender, msg.value);
    }
    
    function withdrawlMoney(address payable _to, uint _amount) public ownerOrallowanceChecker(_amount){
        emit WithdrawMoney(_to, _amount);
        
        require(_amount <= address(this).balance, "Not enough balance");
        if(msg.sender!=owner()){
            reduceAllowance(msg.sender, _amount);
        }
        
        _to.transfer(_amount);
    } 
    
    function seeBalanceinSM() public view returns(uint){
        return address(this).balance;
    }
}