Program

/* calculating pi by throwing stones */

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

#define max 2000			/* number of stones to be thrown */
#define seed 11168			/* seed for number generator */

FILE *output;				/* internal file name*/

main()
{

int i, pi=0;
double x, y, area;
 
output= fopen("pi.dat", "w");		/* external file name */

srand48(seed);				/* seed the number generator */

for (i=1; i<=max; i++)
{
   x= drand48()*2-1;		 	/* creates floats between */
   y= drand48()*2-1;			/* 1 and -1 */
 
   if ((x*x + y*y)<1) pi++;		/* stone hit the pond */
   
   area=4.0*(double) pi/(double) i;	/* calculate area */
   
   fprintf(output, "%i\t%f\n", i, area);
}

fclose (output);
}