AQA · GCSE · Computer Science · Higher

Generating a bounded random number in C#

Q03.1 2 marks

Figure 3 shows an incomplete C# program for a number guessing game. Line numbers are included but are not part of the program.

Figure 3

1	Random rGen = new Random();
2	int randomNumber;
3
4	Console.WriteLine("Enter a number");
5	int userNumber = Convert.ToInt32(Console.ReadLine());
6	while (userNumber < 1 \|\| userNumber > 100)
7	{
8	Console.WriteLine("Invalid number");
9	userNumber = Convert.ToInt32(Console.ReadLine());
10	}
11	Console.WriteLine("Valid number entered");
12	if (randomNumber == userNumber)
13	{
14	Console.WriteLine("Number guessed correctly");
15	}

The program should generate a random number between 1 and 100 (including 1 and 100). Write the C# code that should be used on line 3 in Figure 3 to generate that number and assign it to the appropriate variable. You must use rGen.Next(a, b).

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Marking points

1 Assigns the result to randomNumber.
2 Calls rGen.Next with lower bound 1 and exclusive upper bound 101.

Full-mark answer

randomNumber = rGen.Next(1, 101);

Why this answer loses marks

I used the stated random call with the inclusive maximum as its upper argument.

The call excludes its upper argument, so this would omit the top value in the required range.

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