#include <time.h>
double difftime;

for(.....)
{
   time_t anfang;
   schleife.....
}

time_t ende;
difftime(anfang, ende);
printf(".....gesamtdauer....");

#include <stdio.h>
#include <time.h>

int fibonacci(int x)
{
	if (x<2)
		return 1;
	else
	{
		return (fibonacci(x-1) + fibonacci(x-2));
	}
}

void main(void)
{
	unsigned long k_Kinder;
	int anz = 1;
	time_t start, ende;
	time_t startI, endeI;
	int i;
	unsigned long zahl0=1, zahl1 = 1, erg=1;

	start = clock();
	k_Kinder = fibonacci(anz);
	printf("\n\nREKURSIVE LOESUNG\n\n");
	printf("Anzahl Hasen-Kinder: %u",k_Kinder);
	ende = clock();
	printf("\nZeit in Sek: %lf",(ende*1.0 - start)/CLOCKS_PER_SEC);

	startI = clock();
	printf("\n\nITERATIVE LOESUNG: \n\n");
	
	for (i=2; i <= anz; i++)
	{
		erg = zahl0 + zahl1;
		zahl0 = zahl1;
		zahl1 = erg;
	}
	printf("Anzahl Hasen-Kinder: %u",erg);
	
	endeI = clock();
	printf("\nZeit in Sek: %lf\n\n",(endeI*1.0 - startI)/CLOCKS_PER_SEC);
	
}