Some demo Smart Contract (deploy via https://remix.ethereum.org)

VerrStorage.sol

pragma solidity >=0.4.22 <0.7.0;

/**
 * @title VerrStorage
 * @dev Store & retreive value in a variable
 */
contract VerrStorage {

    address payable public owner = msg.sender;
    uint public creationTime = block.timestamp;

    uint256 number;

    /**
     * @dev Store value in variable
     * @param num value to store
     */
    function store2(uint256 num) public {
        number = num;
    }

    /**
     * @dev Return value 
     * @return value of 'number'
     */
    function retreive() public view returns (uint256){
        return number;
    }
    
    function kill() public { 
        if (msg.sender == owner) 
            selfdestruct(owner); 
    }
}