The malloc() function allocates size bytes of memory.  The allocated
space is suitably aligned (after possible pointer coercion) for storage
of any type of object.  If the space is at least pagesize bytes in length
(see getpagesize((3)),) the returned memory will be page boundary aligned
as well.  If malloc() fails, a NULL pointer is returned.

The calloc() function allocates space for number objects, each size bytes
in length.  The result is identical to calling malloc() with an argument
of ``number * size'', with the exception that the allocated memory is
initialized to nul bytes.

The realloc() function changes the size of the previously allocated memo-
ry referenced by ptr to size bytes.  The contents of the memory are un-
changed up to the lesser of the new and old sizes.  If the new size is
larger, the value of the newly allocated portion of the memory is unde-
fined.  If the requested memory cannot be allocated, NULL is returned and
the memory referenced by ptr is valid and unchanged.  If ptr is NULL, the
realloc() function behaves identically to malloc() for the specified
size.

The free() function causes the allocated memory referenced by ptr to be
made available for future allocations.  If ptr is NULL, no action occurs.