malloc function - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to allocate memory for an integer using malloc.

C

int *ptr = (int *)[1](sizeof(int));

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

Acalloc

Bfree

Csizeof

Dmalloc

Attempts:

3 left

💡 Hint

Common Mistakes

Using free instead of malloc.

Using sizeof as a function to allocate memory.

Using calloc without proper parameters.

The malloc function allocates memory dynamically. Here, it allocates enough space for one integer.

2fill in blank

medium

Complete the code to allocate memory for an array of 5 integers.

C

int *arr = (int *)malloc([1] * sizeof(int));

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

A5

Bint

Cmalloc

Dsizeof(int)

Attempts:

3 left

💡 Hint

Common Mistakes

Using sizeof(int) twice.

Using the type name instead of the number of elements.

Passing malloc as a parameter.

We multiply the number of elements (5) by the size of each element to allocate enough memory for the array.

3fill in blank

hard

Fix the error in the code to correctly allocate memory for a float pointer.

C

float *ptr = (float *)malloc(sizeof([1]));

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

Aint

Bdouble

Cfloat

Dchar

Attempts:

3 left

💡 Hint

Common Mistakes

Using int instead of float inside sizeof.

Using double or char which are different sizes.

Not casting the malloc return.

The size should match the type of pointer you want to allocate memory for. Here, it's float.

4fill in blank

hard

Fill both blanks to allocate memory for an array of 10 doubles and check if allocation succeeded.

C

double *arr = (double *)malloc([1] * sizeof([2]));
if (arr == NULL) {
    printf("Memory allocation failed\n");
}

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

A10

Bfloat

Cdouble

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using 5 instead of 10 for the number of elements.

Using float instead of double for the type.

Not checking if malloc returned NULL.

We allocate memory for 10 elements of type double. The first blank is the number of elements, the second is the type.

5fill in blank

hard

Fill all three blanks to allocate memory for a char array of 20 elements, initialize it with zeros, and check for success.

C

char *buffer = (char *)[1](20, sizeof([2]));
if (buffer == [3]) {
    printf("Allocation failed\n");
}

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

Acalloc

Bchar

CNULL

Dmalloc

Attempts:

3 left

💡 Hint

Common Mistakes

Using malloc instead of calloc when zero initialization is needed.

Checking pointer against 0 instead of NULL.

Using wrong type inside sizeof.

calloc allocates and initializes memory to zero. We allocate 20 chars and check if the pointer is NULL.