Correct and incorrect variable naming conventions in C++

This program example demonstrates the correct and incorrect variable naming conventions in C++

/**
 * @file main.cpp
 * @brief This program demonstrates the correct and incorrect variable naming conventions in C++.
 */

#include <iostream>
using namespace std;

int main() {
    // Correct variable naming conventions
    int number; ///< Variable names can start with a letter
    int Number; ///< Variable names are case sensitive
    string NUMBER; ///< Variable names can be in uppercase
    float number1; ///< Variable names can contain numbers
    bool number_1; ///< Variable names can contain underscores
    int number_1_; ///< Variable names can end with an underscore
    int _number; ///< Variable names can start with an underscore
    int _number_; ///< Variable names can start and end with an underscore
    int _1number; ///< Variable names can contain numbers after an underscore
    int _1_number; ///< Variable names can contain underscores and numbers
    int _1_number_; ///< Variable names can start and end with an underscore and contain numbers
    int number1_; ///< Variable names can end with a number and an underscore

    // Incorrect variable naming conventions
    // int 1number; // Variable names cannot start with a number
    // int number$; // Variable names cannot contain special characters
    // int number one; // Variable names cannot contain spaces
    // int number-one; // Variable names cannot contain special characters
    // int number@; // Variable names cannot contain special characters
    // int number#; // Variable names cannot contain special characters

    return 0;
}

Explanation

The provided C++ code is a simple program designed to illustrate the correct and incorrect conventions for naming variables in C++.

The program begins with the inclusion of the iostream library, which is used for input/output operations. The using namespace std; statement is used to avoid having to prefix standard library components with std::.

#include <iostream>
using namespace std;

The main function is where the execution of the program starts. Inside this function, several variables are declared to demonstrate the correct naming conventions in C++.

int number; ///< Variable names can start with a letter
int Number; ///< Variable names are case sensitive
string NUMBER; ///< Variable names can be in uppercase

In C++, variable names can start with a letter, are case sensitive, and can be in uppercase. They can also contain numbers and underscores. For example, number1, number_1, and number_1_ are all valid variable names.

float number1; ///< Variable names can contain numbers
bool number_1; ///< Variable names can contain underscores
int number_1_; ///< Variable names can end with an underscore

Variable names can also start with an underscore, and they can contain numbers after an underscore. For instance, _number, _1number, and _1_number are all valid variable names.

int _number; ///< Variable names can start with an underscore
int _1number; ///< Variable names can contain numbers after an underscore
int _1_number; ///< Variable names can contain underscores and numbers

The program also includes commented-out lines of code that demonstrate incorrect variable naming conventions. In C++, variable names cannot start with a number, contain special characters, or contain spaces.

// int 1number; // Variable names cannot start with a number
// int number$; // Variable names cannot contain special characters
// int number one; // Variable names cannot contain spaces

Finally, the main function returns 0, indicating successful execution of the program.