001-pragma-solidity.sol

// SPDX-License-Identifier: GPL-3.0

// specify the solidity version you code is currently being written in
// pragma is generally the first line in a solidity file and it is a 
// directive that specifies the compiler version to be used for
// the solidity file

// single version
// pragma solidity 0.8.0;

// range version
pragma solidity >= 0.7.0 < 0.9.0;

// reference for solidity version releases
// Link: https://github.com/ethereum/solidity/releases