#include <stdio.h>
#include <dos.h>

void main(void)
 {
   struct dfree diskinfo;
   long disk_space;

   getdfree(3, &diskinfo);
   disk_space = (long) diskinfo.df_avail * (long) diskinfo.df_bsec * (long) diskinfo.df_sclus;

   printf("Available disk space %ld\n", disk_space);
 }