Standard header files in C

In C language, header files contain the set of predefined standard library functions. The "#include" preprocessing directive is used to include the header files with ".h" extension in the program.

Here is the table that displays some of the header files in C language,

Here is an example of header files in C language,

Example

 Live Demo

#include <stdio.h>
#include<stdlib.h>
#include<string.h>
#include<math.h>

int main() {
   char s1[20] = "53875";
   char s2[10] = "Hello";
   char s3[10] = "World";
   int res;

   res = pow(8, 4);
   printf("Using math.h, The value is : %d\n", res);

   long int a = atol(s1);
   printf("Using stdlib.h, the string to long int : %d\n", a);
   
   strcpy(s2, s3);
   printf("Using string.h, the strings s2 and s3 : %s\t%s\n", s2, s3 );

   return 0;
}

Output

Here is the output −

Using math.h, The value is : 4096
Using stdlib.h, the string to long int : 53875
Using string.h, the strings s2 and s3 : World World