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Basic Calculator Using If Statements in C#

This C# program implements a simple calculator that allows users to perform basic arithmetic operations on two numbers. The program follows a structured approach to prompt the user for input, validate the operation, and compute the result.

How the program works:
1. The user is prompted to enter the first number.
2. The user is prompted to enter an operation (one of +, -, *, x, or /).
3. The user is prompted to enter the second number.
4. The program performs the requested operation using if statements (not switch).
5.The result of the operation is displayed in a structured format.
6. If an invalid operation is entered, the program displays an error message.
7. If division is attempted by zero, the program prevents it and warns the user.

This exercise reinforces conditional statements (if), user input handling, and basic arithmetic operations in C#.



Group

C# Basic Data Types Overview

Objective

Write a C# program that asks the user for two numbers and an operation to perform on them (+, -, *, x, /) and displays the result.

Note: The program MUST use if statements, not switch.

Example C# Exercise

 Copy C# Code 
using System;

class Program
{
    static void Main()
    {
        // Prompt the user to enter the first number
        Console.Write("Enter the first number: ");
        double num1;
        
        // Validate input
        while (!double.TryParse(Console.ReadLine(), out num1))
        {
            Console.Write("Invalid input. Enter a valid number: ");
        }

        // Prompt the user to enter an operation
        Console.Write("Enter operation (+, -, *, x, /): ");
        string operation = Console.ReadLine();

        // Prompt the user to enter the second number
        Console.Write("Enter the second number: ");
        double num2;
        
        // Validate input
        while (!double.TryParse(Console.ReadLine(), out num2))
        {
            Console.Write("Invalid input. Enter a valid number: ");
        }

        double result;
        bool validOperation = true;

        // Perform the chosen operation using if statements
        if (operation == "+")
        {
            result = num1 + num2;
        }
        else if (operation == "-")
        {
            result = num1 - num2;
        }
        else if (operation == "*" || operation == "x")
        {
            result = num1 * num2;
        }
        else if (operation == "/")
        {
            if (num2 == 0) // Prevent division by zero
            {
                Console.WriteLine("Error: Division by zero is not allowed.");
                return;
            }
            result = num1 / num2;
        }
        else
        {
            validOperation = false;
            result = 0;
        }

        // Display the result or an error message for invalid operations
        if (validOperation)
        {
            Console.WriteLine($"{num1} {operation} {num2} = {result}");
        }
        else
        {
            Console.WriteLine("Error: Invalid operation. Please use +, -, *, x, or /.");
        }
    }
}

 Output

//Example 1 (Valid Addition Operation):
Enter the first number: 5
Enter operation: +
Enter the second number: 7
5 + 7 = 12

//Example 2 (Valid Multiplication with ‘x’):
Enter the first number: 8
Enter operation: x
Enter the second number: 3
8 x 3 = 24

//Example 3 (Division Attempt by Zero):
Enter the first number: 10
Enter operation: /
Enter the second number: 0
Error: Division by zero is not allowed.

//Example 4 (Invalid Operation Entered):
Enter the first number: 9
Enter operation: ^
Enter the second number: 2
Error: Invalid operation. Please use +, -, *, x, or /.

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