C# DataType MCQs

Question 16: What is the size of a decimal?

Answer: C

The size of a decimal type is 16 bytes. Learn C# datatypes.

Question 17: Value types are passed by ______ and reference types are passed by _____.

Answer: C

Learn about value types and reference types.

Question 18: What will be the output of the following program?

public static void Main()
{
	string name = "Steve";
	Change(name);
	Console.WriteLine(name);
}
	
static void Change(string str)
{
	str = "Bill";
}

Answer: A

The string is a reference type, and all the reference types are passed by reference. However, the string is immutable, which means once a string is created and stored in a memory, you cannot modify it.

Above, the str parameter in the Change() method points to the same reference when passed the name variable in the Change() method. But, it creates a new string at the new location when changed “Bill”. Thus, name and str point to the different strings after changing str in the Change() method.

Question 19: What will the output of the following program?

   class Program
{
    static void Main(string[] args)
    {
        int myNum = 10;
        ProcessNumber(ref myNum); 
           
        Console.WriteLine(myNum);
        Console.ReadLine();
    }
 
    public static void ProcessNumber(ref int num)
    {
        num = 100;
    }
           
}

Answer: B

The value type variable is passed by value by default. However, when used ref keyword, it will be passed by reference. So, any changes in the callee method will be reflected in the original variable.

Question 20: What will be the output of the following program?

public class Program
{
	public static void Main(string[] args)
 	{
		String str = "Steve";
		object o = "Bill";
		
		Change(str);
		Console.Write(str + ", ");

		Change(o);
		Console.Write(o + ", ");
		
	}

	static void Change(object obj)
	{ 
		obj = obj + " Gates";
	}
		
	static void Change(string str)
	{ 
		str = str + " Jobs";
	}
}

Answer: D

String is a reference type, and all the reference types are passed by reference. It is also immutable, which means once a string is created and stored in a memory, you cannot modify it.

Above, the str parameter in the Change(string str) method actually points to the same location as str in the Main() function. However, when we modify str inside the Change() method, it creates a new string and points to that new memory location. So, str in the Main() and str in the Change() method points to two different strings. And that's why even though the string is a reference type, it doesn't reflect the change that happened inside the Change() method. Learn C# Strings.