Variables & Constants

⚡ C++ Lesson 2 Beginner

C++ is a strongly and statically-typed programming language. Variables must be declared with a specific data type before they are used, allocating concrete space on stack memory frames.

1 Primitive Data Types & Conversions

C++ contains the standard numerical data primitives:

`bool` (1 byte): Stores `true` or `false`.
`char` (1 byte): Stores single character codes.
`int` (4 bytes): Stores standard integers.
`float` (4 bytes): Single-precision floating point.
`double` (8 bytes): Double-precision floating point (default decimals).

Casting: Avoid implicit casting when possible. Use C++ style **`static_cast<type>(val)`** rather than parenthetical C-style casting: `double avg = static_cast<double>(score) / total;`.

2 Variables & Constants Codes

Let's run a program declaring types, casting, and defining constant flags:

C++ — Variables and Casting ▶ Run Code

#include <iostream>

int main() {
    int age = 22;
    double price = 49.99;
    const double TAX_RATE = 0.08; // Cannot be modified later
    
    // Explicit static cast to double
    int score = 45;
    int total = 50;
    double percentage = static_cast<double>(score) / total * 100;

    std::cout << "Age: " << age << "\n";
    std::cout << "Score Percentage: " << percentage << "%" << "\n";
    std::cout << "Tax Rate: " << TAX_RATE << "\n";

    return 0;
}

3 Code Challenge

Challenge: Declare a `const` float variable representing gravity (`9.8f`). Try to reassign its value to `9.81f` inside your code, compile it, observe the compiler error message, and then fix it by removing the invalid assignment statement.