C# Exercise: 53 Calculator - if

using System;  // Import the System namespace to use basic classes like Console

class Program  // Define the main class of the program
{
    static void Main()  // The entry point of the program
    {
        double num1, num2, result;  // Declare variables for two numbers and the result
        string operation;  // Declare a variable to store the operation

        // Ask the user for the first number
        Console.Write("Enter the first number: ");
        num1 = Convert.ToDouble(Console.ReadLine());  // Read and convert the input to double

        // Ask the user for the operation
        Console.Write("Enter operation (+, -, *, x, /): ");
        operation = Console.ReadLine();  // Read the operation as a string

        // Ask the user for the second number
        Console.Write("Enter the second number: ");
        num2 = Convert.ToDouble(Console.ReadLine());  // Read and convert the second number to double

        // Perform the operation using "if"
        if (operation == "+")  // Check if the operation is addition
        {
            result = num1 + num2;  // Perform addition
            Console.WriteLine($"{num1} + {num2} = {result}");  // Display the result
        }
        else if (operation == "-")  // Check if the operation is subtraction
        {
            result = num1 - num2;  // Perform subtraction
            Console.WriteLine($"{num1} - {num2} = {result}");  // Display the result
        }
        else if (operation == "*" || operation == "x")  // Check if the operation is multiplication (consider both '*' and 'x')
        {
            result = num1 * num2;  // Perform multiplication
            Console.WriteLine($"{num1} * {num2} = {result}");  // Display the result
        }
        else if (operation == "/")  // Check if the operation is division
        {
            if (num2 != 0)  // Check if the divisor is not zero
            {
                result = num1 / num2;  // Perform division
                Console.WriteLine($"{num1} / {num2} = {result}");  // Display the result
            }
            else  // If the divisor is zero
            {
                Console.WriteLine("Error: Cannot divide by zero.");  // Display an error message
            }
        }
        else  // If the operation is not recognized
        {
            Console.WriteLine("Invalid operation. Please use +, -, *, x, or /.");  // Display an error message
        }
    }
}