C++ Variables

What is a Variable?

A variable is a named storage location in memory that holds a value. You must declare the variable type before using it.

Syntax

type variableName = value;

Example

#include <iostream>
using namespace std;

int main() {
    int age = 25;
    double price = 9.99;
    char grade = 'A';
    bool isStudent = true;
    string name = "Alex";

    cout << "Name: " << name << endl;
    cout << "Age: " << age << endl;
    cout << "Price: " << price << endl;
    cout << "Grade: " << grade << endl;
    cout << "Student: " << isStudent << endl;
    return 0;
}

Output:

Name: Alex
Age: 25
Price: 9.99
Grade: A
Student: 1

Common Variable Types

Naming Rules

• Names can contain letters, digits, and underscores.
• Must start with a letter or underscore (not a digit).
• Case-sensitive: age and Age are different variables.
• Cannot use C++ reserved keywords (e.g., int, return).

int myAge = 30;       // valid
int _count = 0;       // valid
int 1name = 5;        // INVALID — starts with digit
int int = 10;         // INVALID — reserved keyword

Declare Multiple Variables

int x = 1, y = 2, z = 3;
cout << x + y + z;    // Output: 6

#include <iostream>
using namespace std;

int main() {
    string productName = "Laptop";
    double price = 999.99;
    int quantity = 10;
    bool inStock = true;

    cout << "Product: " << productName << endl;
    cout << "Price: $" << price << endl;
    cout << "Quantity: " << quantity << endl;
    cout << "In Stock: " << inStock << endl;
    return 0;
}

Summary

• Variables are declared as type name = value;
• Common types: int, double, char, bool, string.
• Names are case-sensitive and cannot start with a digit.
• Multiple variables of the same type can be declared on one line.