🔹C++ Variables – Complete Guide for Beginners

🧠 What is a Variable?

A variable in C++ is a named storage location that holds a value.
Think of it like a box with a label that stores information (like numbers or text) while your program runs.

---

📝 Syntax

dataType variableName = value;

📌 Example:

int age = 20;

• int → type of data (integer)
• age → variable name
• 20 → value assigned to the variable

---

🔹 Common Data Types in C++

Data Type	Description	Example
int	Integer numbers	int a = 10;
float	Decimal numbers	float pi = 3.14;
double	Larger decimal numbers	double d = 5.678;
char	Single characters	char grade = 'A';
bool	True or False	bool isOn = true;
string	Text (needs #include <string>)	string name = "Ali";

---

🎯 Example Code

#include <iostream>
#include <string>
using namespace std;

int main() {
    int age = 18;
    float height = 1.75;
    char grade = 'A';
    bool passed = true;
    string name = "Ali";

    cout << "Name: " << name << endl;
    cout << "Age: " << age << endl;
    cout << "Height: " << height << " m" << endl;
    cout << "Grade: " << grade << endl;
    cout << "Passed: " << passed << endl;

    return 0;
}

---

🔐 Rules for Naming Variables

✅ Allowed:

• Letters (a-z, A-Z)
• Digits (0-9)
• Underscore _

❌ Not Allowed:

• Starting with a number (e.g., 2num)
• Special characters (@, #, !, etc.)
• Reserved keywords (like int, return, while)

---

🚀 Pro Tip

You can declare multiple variables of the same type on one line:

int x = 5, y = 10, z = 15;

---

✅ Summary

Concept	Example
Declare	int num;
Initialize	num = 7;
Combined	int num = 7;
Output	cout << num;