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C# Questions & Answers ? Reference Variables and Assignment

C# Questions & Answers – Reference Variables and Assignment

This set of C# Quiz focuses on “Reference Variables and Assignment”.

1. Which reference modifier is used to define reference variable?
a) &
b) ref
c) #
d) $

Answer: b
Explanation: None.

2. What will be the output of the following C# code?

```
   static void Main(string[] args)
```
```
   {
```
```
       int a = 5;
```
```
       fun1 (ref a);
```
```
       Console.WriteLine(a);
```
```
       Console.ReadLine();
```
```
    }
```
```
    static void fun1(ref int a)
```
```
    {
```
```
        a = a * a;
```
```
    }
```

a) 5
b) 0
c) 20
d) 25

Answer: d
Explanation: Here ‘a’ = 5. Copy of variable is passed as reference to parameter ‘a’.
Output:

3. What will be the output of the following C# code?

```
 static void Main(string[] args)
```
```
 {
```

     int[] arr = new int[] {1, 2, 3, 4, 5};

```
     fun1(ref arr);
```
```
     Console.ReadLine();
```
```
  }
```
```
 static void fun1(ref int[] array)
```
```
 {
```

     for (int i = 0; i < array.Length; i++)

```
     {
```
```
         array[i] = array[i] + 5;
```

         Console.WriteLine(array[i] + " ");

```
     }
```
```
 }
```

a) 6 7 8 9 10
b) 15 17 8 8 20
c) 15 17 8 29 20
d) Syntax error while passing reference of array variable

Answer: a
Explanation: array ‘arr’ after declaration is passed as reference parameter.
a[0] = 1 + 5 = 6.
a[1] = 2 + 5 = 7.
.
.
a[4] = 5 + 5 = 10.
Output :

 15 17 8 29 20

4. What will be the output of the following C# code?

```
  static void Main(string[] args)
```
```
  {
```
```
      int a = 10 , b = 20;
```

      Console.WriteLine("Result before swap is: "+ a +" "+b);

```
      swap(ref a, ref b);
```
```
      Console.ReadLine();
```
```
  }
```

  static void swap(ref int i, ref int j)

```
  {
```
```
      int t;
```
```
      t = i;
```
```
      i = j;
```
```
      j = t;
```

      Console.WriteLine("Result after swap is:"+ i +" "+j);

```
  }
```

Result before swap is: 20 10
Result after swap is: 20 10

Result before swap is: 10 20
Result after swap is:20 10

Result before swap is: 10 20
Result after swap is:10 20

Result before swap is: 20 10
Result after swap is:10 20

Answer: b
Explanation: Makes use of call by reference parameter.
Output:

       Result before swap is: 10 20.
       Result after swap is:20 10.

5. What will be the output of the following C# code?

```
 static void Main(string[] args)
```
```
 {
```

     int []a = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

```
     func(ref a);
```
```
     Console.ReadLine();
```
```
 }
```
```
 static void func(ref int[] x)
```
```
 {
```

     Console.WriteLine(" numbers are:");

```
     for (int i = 0; i < x.Length; i++)
```
```
     {
```
```
         if (x[i] % 2 == 0)
```
```
         {
```
```
             x[i] = x[i] + 1;
```
```
             Console.WriteLine(x[i]);
```
```
         }
```
```
     }
```
```
 }
```

a) numbers are : 2 4 6 8 10
b) numbers are : 3 5 7 9 11
c) numbers are : 2 3 4 5 6
d) none of the mentioned

Answer: b
Explanation: Those numbers divisible by 2 are 2, 4, 6, 8, 10 and when condition of loop is executed it increments by 1.
i.e for x[1] = 2%2 == 0.So, x[1] = 2 + 1 = 3.
x[3] = 4%2 == 0.So, x[3] = 4 + 1 = 5 and so on.
Output :

 3 5 7 9 11

6. Select the wrong statement about ‘ref’ keyword in C#?
a) References can be called recursively
b) The ‘ref’ keyword causes arguments to be passed by reference
c) When ‘ref’ are used, any changes made to parameters in method will be reflected in variable when control is passed back to calling method
d) All of the mentioned

Answer: a
Explanation: None.

7. Select correct differences between ‘=’ and ‘==’ in C#.
a)

'==' operator is used to assign values from one variable to another variable
'='  operator is used to compare value between two variables

'=' operator is used to assign values from one variable to another variable
'==' operator is used to compare value between two variables

c) No difference between both operators
d) None of the mentioned

Answer: b
Explanation: None.

8. What will be the output of the following C# code?

```
  static void Main(string[] args)
```
```
  {
```
```
      int X = 0;
```
```
      if (Convert.ToBoolean(X = 0))
```
```
      Console.WriteLine("It is zero");
```
```
      else 
```

      Console.WriteLine("It is not zero");

```
      Console.ReadLine();
```
```
  }
```

a) It is zero
b) It is not zero
c) Infinite loop
d) None of the mentioned

Answer: b
Explanation: The operator ‘=’ used is not comparison operator it is assignment operator. Since value assigned to ‘X’ = 0. So,’0′ value is stored in ‘X’ and with the help of if condition implementation it is converted to ‘false’ which directly means It is not zero but ‘1’ which means ‘true’.

9. What will be the output of the following C# code?

```
    static void Main(string[] args)
```
```
    {
```
```
       int X = 6,Y = 2;
```
```
       X  *= X / Y;
```
```
       Console.WriteLine(X);
```
```
       Console.ReadLine();
```
```
    }
```

a) 12
b) 6
c) 18
d) Compile time error

Answer: c
Explanation: X*=X/Y.
X=x*(X/Y).
Output:

10. What will be the output of the following C# code?

```
    static void Main(string[] args)
```
```
    {
```
```
        int x = 4 ,b = 2;
```
```
        x -= b/= x * b;
```
```
        Console.WriteLine(x + " " + b);
```
```
        Console.ReadLine();
```
```
    }
```

a) 4 2
b) 0 4
c) 4 0
d) 2 2

Answer: c
Explanation: x = x – b and b = b/(x*b).
Output:

4 0

11. What will be the output of the following C# expression?

 int  a+= (float) b/= (long)c.

a) float
b) int
c) long
d) none of the mentioned

Answer: b
Explanation: None.

12. What will be the output of the following C# code?

```
   static void Main(string[] args)
```
```
   {
```
```
       int x = 8;
```
```
       int b = 16;
```
```
       int C = 64;
```
```
       x /= b /= C;
```

       Console.WriteLine(x + " " + b+ " " +C);

```
       Console.ReadLine();
```
```
   }
```

a) 8 2 32
b) 32 4 8
c) 32 2 8
d) Compile time error

Answer: d
Explanation: Exception handling error of dividing by zero.

13. What will be the output of the following C# code?

```
   static void Main(string[] args)
```
```
   {
```
```
       int x = 8;
```
```
       int b = 16;
```
```
       int C = 64;
```
```
       x /= b /= C;
```

       Console.WriteLine(x + " " + b+ " " +C);

```
       Console.ReadLine();
```
```
   }
```

a) 8 2 32
b) 32 4 8
c) 32 2 8
d) Compile time error

Answer: c
Explanation: x / = b / = C is x = x * c /b.
Output:

32 2 8

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