Why dynamic memory is needed - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to allocate memory dynamically for an integer.

C

#include <stdlib.h>

int main() {
    int *ptr = (int*)[1](sizeof(int));
    if (ptr == NULL) {
        return 1;
    }
    *ptr = 10;
    free(ptr);
    return 0;
}

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Amalloc

Bprintf

Csizeof

Dfree

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'sizeof' instead of a memory allocation function.

Forgetting to cast the return value of malloc.

Using 'free' instead of 'malloc' for allocation.

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 dynamically.

C

#include <stdlib.h>

int main() {
    int *arr = (int*)malloc([1] * sizeof(int));
    if (arr == NULL) {
        return 1;
    }
    free(arr);
    return 0;
}

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A10

B0

Csizeof(arr)

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using the size of the pointer instead of the number of elements.

Allocating zero bytes.

Using an incorrect number for the array size.

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

3fill in blank

hard

Fix the error in the code to properly allocate and free memory for a float variable.

C

#include <stdlib.h>

int main() {
    float *ptr = (float*)[1](sizeof(float));
    if (ptr == NULL) {
        return 1;
    }
    *ptr = 3.14f;
    free(ptr);
    return 0;
}

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Amalloc

Bfree

Csizeof

Dcalloc

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'free' instead of 'malloc' for allocation.

Confusing 'sizeof' with allocation functions.

Using 'calloc' without initializing properly.

The malloc function is used to allocate memory. Using free here is incorrect because it deallocates memory.

4fill in blank

hard

Fill both blanks to allocate memory for 10 doubles and check if allocation was successful.

C

#include <stdlib.h>
#include <stdio.h>

int main() {
    double *data = (double*)[1](10 * sizeof(double));
    if (data [2] NULL) {
        printf("Allocation failed\n");
        return 1;
    }
    free(data);
    return 0;
}

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Amalloc

B==

C!=

Dfree

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'free' instead of 'malloc' for allocation.

Checking if pointer equals NULL instead of not equals.

Using '==' instead of '!=' in the condition.

malloc allocates memory. We check if the pointer is not equal to NULL to confirm successful allocation.

5fill in blank

hard

Fill all three blanks to create a dynamic array of chars, assign a value, and free the memory.

C

#include <stdlib.h>
#include <stdio.h>

int main() {
    char *buffer = (char*)[1](20 * sizeof(char));
    if (buffer == NULL) {
        return 1;
    }
    buffer[0] = [2];
    printf("First char: %c\n", buffer[0]);
    [3](buffer);
    return 0;
}

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Amalloc

B'A'

Cfree

Dcalloc

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'calloc' instead of 'malloc' without explanation.

Assigning a string instead of a character.

Forgetting to free the allocated memory.

We use malloc to allocate memory, assign the character 'A' to the first element, and then free the memory with free.