Questions

A primary school teacher wants a program to test their pupils' knowledge of times tables (2 - 12). Read through the code for this problem and answer the following questions.

using System;

namespace timesTable
{
    class Program
    {
        static void Main(string[] args)
        {
           const int NUM_OF_QUESTIONS = 10;
            const int LOWER = 2;
            const int UPPER = 12;
            string name;
            int correct = 0;

            Console.Clear();
            Console.WriteLine("Test: Times Tables");

            Console.Write("What is your name? ");
            name = Console.ReadLine();

            Random rnd = new Random();
            for (int i = 1; i <= NUM_OF_QUESTIONS; i++)
            {
                int first = rnd.Next(LOWER,UPPER);
                int second = rnd.Next(LOWER,UPPER);
                int answer = first * second;
                Console.Write($"{i} : {first} * {second} = ");
                int myAnswer = Convert.ToInt32(Console.ReadLine());
                if (answer == myAnswer)
                {
                    correct++;
                    Console.WriteLine($"Correct! {correct}/{i}");
                }
                else
                {
                    Console.WriteLine($"The correct answer was {answer} ({correct}/{i})");
                }
            }
            Console.WriteLine($"{name}, you scored {correct}!");
            Console.Write("Press any key to quit ...");
            Console.ReadKey();
        }
    }
}

1. Why is it a good idea to use a constant for the number of questions being asked?
2. How are constants different from variables?
3. Explain, with reference to the code, how a random number is being generated.
4. The program uses a loop (see chapter 6). Can you explain how this loop works?
5. Explain the line correct++
6. Modify the code to output the percentage of correct answers
7. Explain what is meant by exception handling, how and where might exception handling be used in this program?

Additional Exercises

1. Using a bitwise operator write a program that checks if an integer is odd or even.
2. The gravitational field of the Moon is approximately 17% that of the Earth. Write a program that calculates your weight on the Moon.
3. Write a program that takes as input a four digit number and calculates the sum of the digits
4. EXTENSION: Write a program that checks if a given number input from the keyboard is a prime number. (This requires a loop.)