C++ Developer - Lesson 2

A variable in C++ is a named container that stores data. You can think of it as a labeled box that holds a value. Every variable has a type, which tells C++ what kind of data it can hold. Common types include int for whole numbers and string for text. You give a variable a name and a value when you declare it. The value can be changed later if needed. Variables let you store, reuse, and manipulate data throughout your program. This lesson will show you how to create and use variables in C++.

#include <iostream>
using namespace std;

int main() {
    int score = 95;
    cout << score;
    return 0;
}

• int score = 95; declares an integer variable named score and gives it the value 95.
• The type int tells C++ that this variable will hold a whole number.
• The equal sign = assigns the value on the right to the variable on the left.
• cout << score; prints the value stored in the variable.
• The output is 95, which is the value of score.

#include <iostream>
using namespace std;

int main() {
    string name = "Alice";
    int age = 12;
    cout << name << " is " << age;
    return 0;
}

• You can declare multiple variables of different types in one program.
• string name = "Alice"; creates a text variable and sets it to Alice.
• int age = 12; creates a number variable and sets it to 12.
• cout << name << " is " << age; prints both variables together.
• The output is Alice is 12.

#include <iostream>
using namespace std;

int main() {
    int points = 10;
    points = 25;
    cout << points;
    return 0;
}

• A variable can be changed after it is declared by assigning a new value.
• int points = 10; creates the variable and sets it to 10.
• points = 25; changes the value to 25, replacing the old value.
• When you print points, it shows the current value, which is 25.
• The old value 10 is gone after the reassignment.

#include <iostream>
using namespace std;

int main() {
    int a = 15;
    int b = 4;
    cout << a + b;
    return 0;
}

• Variables can be used in arithmetic expressions.
• int a = 15; and int b = 4; create two variables.
• cout << a + b; adds their values and prints the result.
• The expression a + b is evaluated to 19 before printing.
• You can use variables anywhere you would use a plain number.

#include <iostream>
using namespace std;

int main() {
    int length = 8;
    int width = 5;
    cout << length * width;
    return 0;
}

• Variables make it easy to perform calculations with named values.
• int length = 8; and int width = 5; store the dimensions.
• cout << length * width; multiplies them to find the area.
• The expression length * width gives 40.
• Using variables makes the code easier to read and change later.

#include <iostream>
using namespace std;

int main() {
    string city = "Paris";
    string country = "France";
    cout << city << ", " << country;
    return 0;
}

• Variables can hold text using the string type.
• string city = "Paris"; stores the text Paris.
• string country = "France"; stores the text France.
• cout << city << ", " << country; prints both strings with a comma between them.
• The output is Paris, France.