C Pointer Basics

Question 1

What is the output of following program?

C

# include <stdio.h>
void fun(int x)
{
    x = 30;
}

int main()
{
  int y = 20;
  fun(y);
  printf(\"%d\", y);
  return 0;
}

• 30
• 20
• Compiler Error
• Runtime Error

Question 2

Output of following program?

C

# include <stdio.h>
void fun(int *ptr)
{
    *ptr = 30;
}

int main()
{
  int y = 20;
  fun(&y);
  printf(\"%d\", y);

  return 0;
}

• 20
• 30
• Compiler Error
• Runtime Error

Question 3

Output of following program?

C

#include <stdio.h>

int main()
{
    int *ptr;
    int x;

    ptr = &x;
    *ptr = 0;

    printf(\" x = %d\\n\", x);
    printf(\" *ptr = %d\\n\", *ptr);

    *ptr += 5;
    printf(\" x  = %d\\n\", x);
    printf(\" *ptr = %d\\n\", *ptr);

    (*ptr)++;
    printf(\" x = %d\\n\", x);
    printf(\" *ptr = %d\\n\", *ptr);

    return 0;
}

• x = 0
  *ptr = 0
  x = 5
  *ptr = 5
  x = 6
  *ptr = 6
  
• x = garbage value
  *ptr = 0
  x = garbage value
  *ptr = 5
  x = garbage value
  *ptr = 6
• x = 0
  *ptr = 0
  x = 5
  *ptr = 5
  x = garbage value
  *ptr = garbage value
• x = 0
  *ptr = 0
  x = 0
  *ptr = 0
  x = 0
  *ptr = 0

Question 4

Consider a compiler where int takes 4 bytes, char takes 1 byte and pointer takes 4 bytes.

C

#include <stdio.h>

int main()
{
    int arri[] = {1, 2 ,3};
    int *ptri = arri;

    char arrc[] = {1, 2 ,3};
    char *ptrc = arrc;

    printf(\"sizeof arri[] = %d \", sizeof(arri));
    printf(\"sizeof ptri = %d \", sizeof(ptri));

    printf(\"sizeof arrc[] = %d \", sizeof(arrc));
    printf(\"sizeof ptrc = %d \", sizeof(ptrc));

    return 0;
}

• sizeof arri[] = 3 sizeof ptri = 4 sizeof arrc[] = 3 sizeof ptrc = 4
• sizeof arri[] = 12 sizeof ptri = 4 sizeof arrc[] = 3 sizeof ptrc = 1
• sizeof arri[] = 3 sizeof ptri = 4 sizeof arrc[] = 3 sizeof ptrc = 1
• sizeof arri[] = 12 sizeof ptri = 4 sizeof arrc[] = 3 sizeof ptrc = 4

Question 5

Assume that float takes 4 bytes, predict the output of following program.

C

#include <stdio.h>

int main()
{
    float arr[5] = {12.5, 10.0, 13.5, 90.5, 0.5};
    float *ptr1 = &arr[0];
    float *ptr2 = ptr1 + 3;

    printf(\"%f \", *ptr2);
    printf(\"%d\", ptr2 - ptr1);

   return 0;
}

• 90.500000 3
• 90.500000 12
• 10.000000 12
• 0.500000 3

Question 6

C

#include<stdio.h>
int main()
{
    int arr[] = {10, 20, 30, 40, 50, 60};
    int *ptr1 = arr;
    int *ptr2 = arr + 5;
    printf(\"Number of elements between two pointer are: %d.\", 
                                (ptr2 - ptr1));
    printf(\"Number of bytes between two pointers are: %d\",  
                              (char*)ptr2 - (char*) ptr1);
    return 0;
}

Assume that an int variable takes 4 bytes and a char variable takes 1 byte

• Number of elements between two pointer are: 5. Number of bytes between two pointers are: 20
• Number of elements between two pointer are: 20. Number of bytes between two pointers are: 20
• Number of elements between two pointer are: 5. Number of bytes between two pointers are: 5
• Compiler Error
• Runtime Error

Question 7

C

#include<stdio.h> 
int main() 
{ 
   int a; 
   char *x; 
   x = (char *) &a; 
   a = 512; 
   x[0] = 1; 
   x[1] = 2; 
   printf(\"%d\\n\",a);   
   return 0; 
}

What is the output of above program?

• Machine dependent
• 513
• 258
• Compiler Error

Question 8

C

int main()
{
 char *ptr = \"GeeksQuiz\";
 printf(\"%c", *&*&*ptr);
 return 0;
}

• Compiler Error

• Garbage Value

• Runtime Error

• G

Question 9

C

#include<stdio.h>
void fun(int arr[])
{
  int i;
  int arr_size = sizeof(arr)/sizeof(arr[0]);
  for (i = 0; i < arr_size; i++)
      printf(\"%d \", arr[i]);
}

int main()
{
  int i;
  int arr[4] = {10, 20 ,30, 40};
  fun(arr);
  return 0;
} 

• 10 20 30 40
• Machine Dependent
• 10 20
• Northing

Question 10

The reason for using pointers in a C program is

• Pointers allow different functions to share and modify their local variables.

• To pass large structures so that complete copy of the structure can be avoided.

• Pointers enable complex “linked" data structures like linked lists and binary trees.

• All of the above