Question

How can a 2D array be allocated using malloc() and a pointer to pointer in C?

a) Using a single call to malloc() for total elements
b) Allocating rows first, then columns using malloc()
c) Using pointer arithmetic for 2D array allocation
d) Using a loop for row-wise allocation using malloc()

Answer 1

To allocate a 2D array in C using malloc() and pointer to pointer, you can use a single call to malloc() for all elements, allocate memory for rows first and then for columns, use pointer arithmetic, or use a loop for row-wise allocation.

Step-by-step explanation:

The question is about how to allocate a 2D array dynamically in C using malloc() and a pointer to pointer approach.

Options for Allocating 2D Arrays:

1. Using a single call to malloc() for the total number of elements. This involves calculating the total size by multiplying the number of rows by the number of columns and allocating a single contiguous block of memory. However, access to elements requires manual computation of indices.

2. Allocating rows first, then columns using malloc(). This means allocating memory for the row pointers initially and then for each row, allocating memory for the columns individually. This allows a more natural array access syntax but requires multiple calls to malloc().

3. Using pointer arithmetic for 2D array allocation. This is less common and not as straightforward as the other methods. It involves manual offset calculation to access elements.

4. Using a loop for row-wise allocation using malloc(). This combines the above methods, where each row is allocated individually in a loop, which then allows for the 2D array to be used as expected with array syntax.