C Pointers 17May2023

How do you access the content of the pointer variable p inside the C program?

# include <stdio.h>

void fun(int x)

{     x = 30; }

 

int main()

{

  int y = 20;

  fun(y);

  printf("%d", y);

  return 0;

}

• 20, as the function call uses Call by value

• 20, as the function call uses Call by reference

• 30, as the function call changes the value

• Error in this code

# include <stdio.h>

void fun(int *ptr)

{     *ptr = 30; }

 

int main()

{

  int y = 20;

  fun(&y);

  printf("%d", y);

 

  return 0;

}

• 30, as the function call is by Call by reference (i.e. call by address)

• 30, as the function call is by Call by value

• 20, as the variable ptr has scope local to the function

• Compile time error

#include <stdio.h>

int main() {

int *ptr;

int x=5;

ptr = &x;

*ptr = 0;

printf("%d\n", x);

return 0;

}

#include <stdio.h>

int main() {

int *ptr;

int x=0;

ptr = &x;

*ptr = 10;

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

return 0;

}

• 10 10

• 10 0

• 0 10

• 10 Undefined

#include <stdio.h>

int main() {

int *ptr;

int x=10;

ptr = &x;

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

*ptr += 5;

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

return 0;

}

• 10 10 15 15

• 10 10 10 15

• 10 10 15 Undefined

• Error

#include <stdio.h>

int main() {

int *ptr;

int x=5, y;

ptr = &x;

y = x;

(*ptr)++;

printf("%d\t %d\n", x, y);

return 0;

}

• 6 5

• 5 6

• Undefined 5

• 6 undefined

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

#include <stdio.h>

 

int main()

{

    int arr_i[] = {1, 2 ,3};

    int *pi = arr_i;

 

    char arr_c[] = {1, 2 ,3};

    char *pc = arr_c;

 

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

    printf("sizeof ptri = %d ", sizeof(pi));

 

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

    printf("sizeof ptrc = %d ", sizeof(pc));

 

    return 0;

}

• 12 4 3 4

• 12 12 3 3

• 3 4 3 4

• 12 4 12 4

#include <stdio.h>

int main()

{

    float arr[5] = {12.5, 10.5, 13.5, 80.5, 70.5};

    float *ptr1 = &arr[0];

    float *ptr2 = ptr1 + 3;

     printf("%f", *ptr2);

return 0;

}

#include <stdio.h>

int main() {

char *x = "Wednesday";

printf("%c %c", x, (x+5));

return 0;

}

• W s

• W Undefined

• W d

• Wednesday Undefined