Разница между рекурсивной функцией и обычной

#include <time.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/timeb.h>
#include <string.h>
 
int main()
{
    char tmpbuf[128], timebuf[26], ampm[] = "AM";
    time_t ltime;
    struct _timeb tstruct;
    struct tm today, gmt, xmas = { 0, 0, 12, 25, 11, 93 };
    errno_t err;
 
    
    // Get UNIX-style time and display as number and string. 
    time( &ltime );
    printf( "Time in seconds since UTC 1/1/70:\t%ld\n", ltime );
    err = ctime_s(timebuf, 26, &ltime);
    if (err)
    {
       printf("ctime_s failed due to an invalid argument.");
       exit(1);
    }
    printf( "UNIX time and date:\t\t\t%s", timebuf );
 
  }

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
 
void sleep( clock_t wait );
 
int main( void )
{
   long    i = 6000000L;
   clock_t start, finish;
   double  duration;
 
   // Delay for a specified time.
   printf( "Delay for three seconds\n" );
   sleep( (clock_t)3 * CLOCKS_PER_SEC );
   printf( "Done!\n" );
 
   // Measure the duration of an event.
   printf( "Time to do %ld empty loops is ", i );
   start = clock();
   while( i-- ) 
      ;
   finish = clock();
   duration = (double)(finish - start) / CLOCKS_PER_SEC;
   printf( "%2.1f seconds\n", duration );
}
 
// Pauses for a specified number of milliseconds.
void sleep( clock_t wait )
{
   clock_t goal;
   goal = wait + clock();
   while( goal > clock() )
      ;
}