Writing a smart contract

A contract is declared using the contract keyword, along with an identifier, as shown in the following code snippet:

contract SampleContract {
}

Within the brackets comes the declaration of state variables and function definitions. Chapter 3, Introducing Solidity, introduced a smart contract that contained almost all important constructs to build a smart contract. The same contract is shown again for quick reference. This contract has state variables, struct definitions, enum declarations, function definitions, modifiers, and events. State variables, structs, and enums were discussed in detail in Chapter 4, Global Variables and Functions. Functions, modifiers, and events will be discussed in detail over the next two chapters. Take a look at the following code listing depicting the contract:

// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.7.0 <0.9.0;
contract GeneralStructure { 
int public stateIntVariable; 
string stateStringVariable...