Variable declaration and initialization in C++

Introduction

Variables store information so your program can use it later. Declaration tells the computer about the variable, and initialization gives it a starting value.

When you want to remember a number, like a score in a game.

When you need to store a name or word to use later.

When you want to keep track of a setting or choice.

When you want to prepare a place to store data before using it.

When you want to update or change information during the program.

Syntax

C++

type variableName = value;

// Example:
int age = 25;

type is the kind of data (like int for numbers, char for letters).

You can declare a variable without giving it a value first, but it's safer to initialize it right away.

Examples

This creates a variable named number that holds an integer value 10.

C++

int number = 10;

This creates a variable price that holds a decimal number.

C++

double price = 9.99;

This creates a variable letter that holds a single character.

C++

char letter = 'A';

This creates a variable isOpen that holds a true/false value.

C++

bool isOpen = true;

Sample Program

This program shows how to declare and initialize different types of variables, then print their values.

C++

#include <iostream>

int main() {
    int age = 30; // Declare and initialize an integer variable
    double height = 1.75; // Declare and initialize a double variable
    char grade = 'B'; // Declare and initialize a char variable
    bool isStudent = false; // Declare and initialize a bool variable

    std::cout << "Age: " << age << "\n";
    std::cout << "Height: " << height << " meters\n";
    std::cout << "Grade: " << grade << "\n";
    std::cout << "Is student: " << isStudent << "\n";

    return 0;
}

Important Notes

In C++, bool variables print as 1 (true) or 0 (false) when using std::cout.

Always choose the right type for your data to avoid errors.

Initializing variables helps prevent unexpected values.

Summary

Variables hold data your program uses.

Declaration tells the program about the variable's type and name.

Initialization gives the variable its first value.