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

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

   if (_dos_getdiskfree(0, &diskinfo))
     printf("Error accessing drive C:\n");
   else
     {
       disk_space = (long) diskinfo.avail_clusters *     
                    (long) diskinfo.bytes_per_sector *
                    (long) diskinfo.sectors_per_cluster;

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