#include <stdio.h>
#include <stdlib.h>

int main()
{
  int      i_vec[20];
  double   d_vec[20];
  const int N_LINES = 20;
  int line;

  /* fp is a pointer to the object controlling the stream. */
  FILE   *fp;

  /* Open the file, named infile, using read-only mode. */
  if ((fp = fopen("infile", "r")) == NULL) {
    printf("Problems opening file infile.\n");
    exit(1);
  }

  for(line = 0; line < N_LINES; line++) 
    fscanf(fp, "%d %lf", &i_vec[line], &d_vec[line]);

  /* Close file. */
  fclose(fp);                       

/* ------------------------------------------------
   If we don't know the number of lines in the file
   we can do like this. Note that i_vec and d_vec
   MUST have room for the elements.
*/

  if ((fp = fopen("infile", "r")) == NULL) {
    printf("Problems opening file infile.\n");
    exit(1);
  }

  line = 0;
  while( fscanf(fp, "%d %lf", &i_vec[line], &d_vec[line]) != EOF)
    line++;

  fclose(fp);                       
  printf("# of lines = %d\n", line);

  /* Start computing ... */

  return 0;
}