C# Question & Answers - Pointers Operation - 2

This set of C# Multiple Choice Questions & Answers (MCQs) focuses on “Pointers Operation – 2”.

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

```
class UnsafeCode
```
```
{
```
```
    struct MyStruct
```
```
    {
```
```
        public int a;
```
```
        public int b;
```
```
        public int Sum() 
```
```
       { 
```
```
           return a * b; 
```
```
       }
```
```
   }
```
```
   unsafe static void Main()
```
```
   {
```
```
       MyStruct o = new MyStruct();
```
```
       MyStruct* p; 
```
```
       p = &o;
```
```
       p->a = 10; 
```
```
       p->b = 20; 
```

       Console.WriteLine("Value is " + p->Sum());

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

a) Compile time error
b) Run time error
c) 200
d) 30
View Answer

Answer: c
Explanation: A pointer can point to an object of a structure type as long as the structure does not contain reference types. When we access a member of a structure through a pointer, we must use the arrow operator, which is –>, rather than the dot (.) operator.
Output : 200

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

```
class UnsafeCode
```
```
{
```
```
    struct MyStruct
```
```
    {
```
```
        public int a;
```
```
        public int b;
```
```
        public int Sum() 
```
```
       { 
```
```
           return a / b; 
```
```
       }
```
```
   }
```
```
   unsafe static void Main()
```
```
   {
```
```
       MyStruct o = new MyStruct();
```
```
       MyStruct* p; 
```
```
       p = &o;
```
```
       p->a = 60; 
```
```
       p->b = 15; 
```
```
       int c = 30;
```

       Console.WriteLine("Value is : " + p->Sum()*c);

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

a) Compile time error
b) 120
c) Run time error
d) 4
View Answer

Answer: b
Explanation: None.
Output :

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

```
class UnsafeCode
```
```
{
```
```
    unsafe static void Main()
```
```
    {
```
```
        int[] nums = new int[10];
```

        fixed (int* p = &nums[0], p2 = nums)

```
        {
```
```
            if (p == p2)
```

            Console.WriteLine("p and p2 point to same address.");

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

a) Run time error
b) Compile time error
c) p and p2 point to the same address
d) Only p2
View Answer

Answer: c
Explanation: None.
Output:

p and p2 point to same address

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

```
class UnsafeCode
```
```
{
```
```
    static void Main()
```
```
    {
```
```
        int? count = null;
```
```
        int? result = null;
```
```
        int incr = 10;
```
```
        result = count + incr;
```
```
        if (result.HasValue)
```

            Console.WriteLine("result has this value: " + result.Value);

```
        else
```

            Console.WriteLine("result has no value");

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

a) Run time error
b) 0
c) Result has no value
d) Compile time error
View Answer

Answer: c
Explanation: A nullable object can be used in expressions that are valid for its underlying type. When non-nullable and nullable types are mixed in an operation, the outcome is a nullable value.
Output:

result has no value

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

```
class UnsafeCode
```
```
{
```
```
    static void Main()
```
```
    {
```
```
        int count = 100;
```
```
        int? result = null;
```
```
        int incr = 10;
```
```
        result = count + incr;
```
```
        if (result.HasValue)
```

            Console.WriteLine("result has this value: " + result.Value);

```
        else
```

            Console.WriteLine("result has no value");

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

a) Run time error
b) 110
c) Result has no value
d) Compile time error
View Answer

Answer: b
Explanation: None.
Output: result has this value :

6. Choose the statement which defines the Nullable type Correctly:
a) A special version of a value type that is represented by a structure
b) A nullable type can also store the value null
c) Nullable types are objects of System.Nullable, where T must be a non nullable value type
d) All of the mentioned
View Answer

Answer: d
Explanation: A nullable type is a special version of the value type that is represented by a structure. In addition to the values defined by the underlying type, a nullable type can also store the value null. Thus, a nullable type has the same range and characteristics as its underlying type. It simply adds the ability to represent a value which indicates that a variable of that type is unassigned. Nullable types are objects of System.Nullable<T>, where T must be a nonnullable value type.

7. What does the following code depicts?

   i. System.Nullable count;
   ii. bool? done;

a) Code i declares the objects of nullable of type Nullable<T> defined in the System namespace
b) Code ii declares a nullable type in much shorter and in more commonly used way using ‘?’
c) Both Code i declares the objects of nullable of type Nullable<T> defined in the System namespace & Code ii declares a nullable type in much shorter and in more commonly used way using ‘?’
d) None of the mentioned
View Answer

Answer: c
Explanation: None.

8. Which operator is commonly used to find the size of the type of C#?
a) size()
b) sizeof(type)
c) both size() & sizeof(type)
d) none of the mentioned
View Answer

Answer: b
Explanation: None.

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

```
 unsafe struct FixedBankRecord
```
```
 {
```
```
     public fixed byte Name[80]; 
```
```
     public double Balance;
```
```
     public long ID;
```
```
 }
```
```
 class UnsafeCode
```
```
 {
```
```
     unsafe static void Main()
```
```
     {
```

         Console.WriteLine("Size of FixedBankRecord is " + sizeof(FixedBankRecord));

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

a) Run time error
b) 80
c) 96
d) Compile time error
View Answer

Answer: c
Explanation: The purpose of a fixed-size buffer is to allow the creation of a struct in which the array of elements that make up the buffer are contained within the struct. By using a fixed-size buffer, we let the entire array to be contained within the struct. The overall size of FixedBankRecord is 96, which is the sum of its members.
Output :

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

```
class UnsafeCode
```
```
{
```
```
    unsafe static void Main()
```
```
    {
```
```
        int* ptrs = stackalloc int[3];
```
```
        ptrs[0] = 1;
```
```
        ptrs[1] = 2;
```
```
        ptrs[2] = 3;
```
```
        for (int i = 2; i >=0; i--)
```
```
        Console.WriteLine(ptrs[i]);
```
```
        Console.ReadLine();
```
```
    }
```
```
}
```

a) 3 2 1
b) 1 2 3
c) None of the mentioned
d) Run time error
View Answer

Answer: a
Explanation: Allocates memory from the stack by using stackalloc. Here, ptrs is a pointer that receives the address of the memory that is large enough to hold size of number of objects of type ‘int’. Here, type ‘int’ is a non reference type. Finally, stackalloc can be used only in an unsafe context.
Output :

3 2 1

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