What is realloc() function ?

To reallocate the memory space we use a function known as realloc(). The realloc() is a function that reallocate a block of memory space that previously allocated by malloc() function.  

In other word, to modified the size of memory that previously allocated by the malloc() function use a realloc() function that modify the size of block of memory space according to requirements.

Sy:

pointer = realloc( pointer, new_size );