Common pointer errors - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a pointer to an integer.

C

int [1] ptr;

Drag options to blanks, or click blank then click option'

A*

B&

C->

D%

Attempts:

3 left

💡 Hint

Common Mistakes

Using & instead of * to declare a pointer.

Confusing pointer declaration with address-of operator.

The asterisk (*) is used to declare a pointer variable in C.

2fill in blank

medium

Complete the code to assign the address of variable x to pointer p.

C

int x = 10;
int *p;
p = [1]x;

Drag options to blanks, or click blank then click option'

A*

B&

C%

D->

Attempts:

3 left

💡 Hint

Common Mistakes

Using * instead of & when assigning address to pointer.

Trying to assign the value instead of the address.

The & operator gives the address of a variable, which can be assigned to a pointer.

3fill in blank

hard

Fix the error in the code to correctly access the value pointed by p.

C

int x = 5;
int *p = &x;
int y = [1]; 

Drag options to blanks, or click blank then click option'

Ap*

Bp

C&p

D*p

Attempts:

3 left

💡 Hint

Common Mistakes

Using the pointer variable itself instead of dereferencing it.

Using & operator which gives the address, not the value.

The * operator is used to dereference a pointer and access the value it points to.

4fill in blank

hard

Fill both blanks to create a pointer to an array and access its first element.

C

int arr[3] = {1, 2, 3};
int [1] p = arr;
int first = [2]; 

Drag options to blanks, or click blank then click option'

A*

B&

Cp[0]

D[]

Attempts:

3 left

💡 Hint

Common Mistakes

Using & instead of * to declare pointer.

Trying to dereference pointer incorrectly.

Declaring *p makes p a pointer. Accessing p[0] gets the first element of the array.

5fill in blank

hard

Fill all three blanks to correctly allocate memory, assign value, and free it.

C

#include <stdlib.h>

int *p = (int*)[1](sizeof(int));
*p = [2];
[3](p);

Drag options to blanks, or click blank then click option'

Amalloc

B42

Cfree

Dsizeof

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to cast malloc's return value.

Not freeing allocated memory causing memory leaks.

Assigning value to pointer instead of dereferenced pointer.

malloc allocates memory, 42 is assigned to the allocated space, and free releases the memory.