C Aptitude Questions And Answers - POINTER

---------------------------------- Test Your "C" Skill -------------------------------------

  POINTERS

1.Can you combine the following two statements into one

char *p;

p=malloc(100);

Output: char *p=malloc(100);

2.Can you split the following statement into two statements?

Char far *str=(char far*) 0xb8000000L;

Output:

char far *str;

str=(char far*) 0xb8000000L;

3.Are the expressions *ptr++ and ++*ptr same?

Output: No.

*ptr++ increments the pointer and not the value pointed by it, 

whereas ++*ptr increments the value being pointed to by ptr.

4. Can You write another expression which does the same job as ++*ptr?

Output:  (*ptr)++

5.What would be the equivalent pointer expression for referring the same element as a[i][j][k][l]?

Output:   *(*(*(*(a+i)+j)+k)+l)

6.

void main()

{

  int arr[]=(12,13,14,15,16};

  printf(“\n%d %d %d”,sizeof(arr),sizeof(*arr),sizeof(arr[0]));

}

Output: 10 2 2

7.What would be the O/P of the program assuming that the array begins at 1002?

void main()

{

  int a[3][4]={

                       1,2,3,4,

                       5,6,7,8,

                       9,10,11,12

                   };

     printf(“\n%u %u %u”,a[0]+1,*(a[0]+1),*(*(a+0)+1));

}

Output: 1004 2 2

8.What would be the output of the program assuming that the array begins at location 1002?

void main()

{

  int a[2][3][4]={

                           {

                               1,2,3,4,

                               5,6,7,8,

                               9,1,1,2

                           },

                          {

                              2,1,4,7,

                              6,7,8,9,

                              0,0,0,0

                          }

                      }

 printf(“\n %u  %u  %u  %d”,a,*a,**a,***a);

 Output:1002  1002  1002  1

9.In the following program how would you print 50 using p?

void main()

{

  int a[]={10,20,30,40,50}

  char *p;

  p=(char*)a;

}

Output: printf(“\n %d”,*((int*)p+4));

10.In the following program add a statement in the function fun() such that the address of  a  gets stored in j.

void main()

{

  int *j;

  void fun(int**);

  fun(&j);

}

void fun(int**k)

{

  int a=10;

 /* add statement here*/

}

Output:  *k=&a;

11.Where can one think of using pointers?

Output: 

--Accessing array or string elements

--Dynamic memory allocation

-- Call by reference

-- Implementing linked lists, trees, graphs, and many other data structures

 Etc.

12.How would you implement an array of three function pointers where each function receives two int and return a float?

Output: float (*arr[3])(int,int);

14. Would the following program give a compilation error or warning?

void main()

{

  float i=10,*j;

  void *k;

  k=&i;

  j=k;

  printf(“\n%f”,*j);

}

Output: No. 

Here no type casting is required while assigning the value to and from k because conversions are applied automatically when other pointer types are assigned to and from void*.

15. Would the following program compile?

void main()

{

  int a=10,*j;

  void *k;

  j=k=&a;

  j++;

  k++;

  printf(“\n %u  %u”,j,k);

}

Output:-void pointers is not permitted unless the void pointer is appropriately type casted.

  

16. Would the following code compile successfully?

void main()

{

  printf(“%c”,7[“ItChallengers”]);

}

Output: YES.

 Prints e of ItChallengers.