4

it can have any number of header files. but it ha smore 
than 8 header files.

there are manynumber hedder files because each hedder file
is used for different purpose.
for example if we are using pointers we will include
different hedder files with the standard hedder files as
#include<stdio.h>

#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
#include<math.h>
#include<graphic.h>
#include<string.h>
#include<ctype.h>
#include<malloc.h>
#include<calloc.h>
#include<sound.h>

Above list are few header file in C. And many more header 
file in C language.

32

10 header files in c.

26 header files in C language.

Is there any valid reason where the limit is deceided.

the following are some of the header files in c:
#include<stdio.h>
#include<string.h>
#include<math.h>
#include<stdlib.h>
#include<floats.h>
#include<conio.h>
#include<time.h>
#include<limits.h>
#include<graphic.h>
#include<ctype.h>
#include<malloc.h>
#include<calloc.h>
#include<sound.h>
there are about 32 header files in c

#include<stdio.h>
#include<conio.h>
#include<math.h>
#include<string.h>
#include<malloc.h>
#include<process.h>
#include<time.h>
#include<calloc.h>
#include<graphic.h>
#include<limits.h>

iso c standard has 24 hederfiles...

around 270 files

17 header files is in c programming.

there are total 24 header files in C.
15 according to C89 & 9 further added in C99.
therefore, total 24.