Variables in C++

 In C++, a variable is a named storage location in the computer's memory that can hold a value. Think of it as a container that can store different types of data.

Key characteristics of variables in C++:

• Name: Each variable has a unique name, called an identifier, which is used to refer to it in the code.
• Type: Every variable has a specific data type that determines the kind of values it can store (e.g., integers, floating-point numbers, characters) and the amount of memory it occupies.
• Value: The data stored in the variable. This value can be changed during the program's execution.

How to declare a variable:

To use a variable in C++, you must first declare it. The declaration specifies the variable's type and name. Here's the basic syntax:

C++

data_type variable_name;

Examples:

C++

int age;         // Declares an integer variable named 'age'
double price;    // Declares a double-precision floating-point variable named 'price'
char initial;    // Declares a character variable named 'initial'
std::string name; // Declares a string variable named 'name'

How to initialize a variable:

You can assign an initial value to a variable at the time of declaration. This is called initialization.

Examples:

C++

int age = 25;           // Declares an integer variable 'age' and initializes it to 25
double price = 19.99;    // Declares a double variable 'price' and initializes it to 19.99
char initial = 'J';      // Declares a char variable 'initial' and initializes it to 'J'
std::string name = "John Doe"; // Declares a string variable and initializes it to "John Doe"

Basic Data Types in C++:

C++ provides several built-in data types:

• int: For storing integers (whole numbers).
• float: For storing single-precision floating-point numbers (numbers with decimal points).
• double: For storing double-precision floating-point numbers (more precise decimal numbers).
• char: For storing single characters (letters, symbols, etc.).
• bool: For storing boolean values (true or false).
• std::string: For storing sequences of characters (text).

Rules for naming variables:

• Variable names can contain letters (uppercase and lowercase), digits, and underscores.
• They must begin with a letter or an underscore.
• They cannot be the same as C++ keywords (e.g., int, float, if, for).
• Variable names are case-sensitive (myVariable is different from myvariable).

Example program:

C++

#include <iostream>
#include <string>

int main() {
    int age = 30;
    double height = 5.9;
    std::string name = "Alice";

    std::cout << "Name: " << name << std::endl;
    std::cout << "Age: " << age << std::endl;
    std::cout << "Height: " << height << std::endl;

    return 0;
}

This program declares and initializes three variables (age, height, and name) and then prints their values to the console.

Variables are fundamental to programming in C++. They allow you to store and manipulate data within your programs. By understanding how to declare, initialize, and use variables effectively, you can write more complex and powerful C++ programs.