Visibility.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.17;
contract Base {
 // Private function can only be called
 // - inside this contract
 // Contracts that inherit this contract cannot call this function.
 function privateFunc() private pure returns (string memory) {
 return "private function called";
 }
function testPrivateFunc() public pure returns (string memory) {
 return privateFunc();
 }
// Internal function can be called
 // - inside this contract
 // - inside contracts that inherit this contract
 function internalFunc
() internal pure returns (string memory) {
 return "internal function called";
 }
function testInternalFunc() public pure virtual returns (string memory) {
 return internalFunc();
 }
// Public functions can be called
 // - inside this contract
 // - inside contracts that inherit this contract
 // - by other contracts and accounts
 function publicFunc() public pure returns (string memory) {
 return "public function called";
 }
// External functions can only be called
 // - by other contracts and accounts
 function externalFunc() external pure returns (string memory) {
 return "external function called";
 }
// This function will not compile since we're trying to call
 // an external function here.
 // function testExternalFunc() public pure returns (string memory) {
 // return externalFunc();
 // }
// State variables
 string private privateVar = "my private variable";
 string internal internalVar = "my internal variable";
 string public publicVar = "my public variable";
 // State variables cannot be external so this code won't compile.
 // string external externalVar = "my external variable";
}