ptrdiff_t - count of elements or array index

       Used  for a count of elements, or an array index.  It is the result of subtracting two pointers.  It is a
       signed integer type capable of storing values in the range [PTRDIFF_MIN, PTRDIFF_MAX].

       The length modifier for ptrdiff_t for the  printf(3)  and  the  scanf(3)  families  of  functions  is  t,
       resulting commonly in %td or %ti for printing ptrdiff_t values.

       C89, POSIX.1-2001.

       Standard C library (libc)

       ptrdiff_t - count of elements or array index

size_t(3type)

Linux man-pages 6.9.1                              2024-05-02                                   ptrdiff_t(3type)

       C11, POSIX.1-2008.

#include<stddef.h>typedef /* ... */  ptrdiff_t;