/* Filename     :   leap.c
 * Function Name:   main
 * Written By   :   Prof. Kantila [kantila@gmail.com]
 * Dated        :   11th Dec 2006
 * Modified on  :   18th Dec 2006
 * Purpose      :   Program to find out leap year in given range
 * Arguments    :   None, Ask interactively
 * Header files :   stdio.h, leap.h
 */
#include <stdio.h>  /*Standard Input/Output functions required */
#include "leap.h"   /*leapf function is defined in this file   */

#define  COLS    5  /*Defining number of columns to be displayed 1-8*/
/*main function, return integer but takes no argument*/
int main(void)
{
    /*Declaration of local variables to hold data */
    long int y1=0,y2=0,current,max,counter=0;
    /*Using unformated output function fputs, it takes two arguments,
      first is string and second in of type FILE *, here stderr*/
    fputs("This will display the leap years in the given range...\n",stderr);
    /*Using formatted output function fprintf, it takes one more argument
      than printf as the first argument of the type FILE *, here stderr*/
    do
    {
     fprintf(stderr,"Input first year of range [1 - 999999999] : ");
     /*Using formatted input function fscanf to read an integer value from
      standard input stream, i.e. stdin - it also takes one more argument than
      scanf function as the first argument of type FILE * */
      fscanf(stdin,"%9li",&y1);
      if(y1<=0)
          fprintf(stderr,"Invalid year!\a\a\n");
      /*fflush(FILE *) function clears (flushes) the specified stream
      This is used here to remove any unwanted data (garbage) from stdin stream*/
      fflush(stdin);
     } while(y1<=0);
    while(1)
    { 
     fprintf(stderr,"Input last  year of range [1 - 999999999] : ");
     fscanf(stdin,"%9li",&y2);
     if(y2<=0)
          fprintf(stderr,"Invalid year!\a\a\n");
     else
         break;
     fflush(stdin);
     /*Conditional operator is used to assign smaller year value to current
      and larger one to max variable so that years can be displayed in increasing
      order */
    }
    (y1<y2)?(current=y1,max=y2):(current=y2,max=y1);
    /*Displaying message on standard output terminal - it may be redirected */
    fprintf(stdout,"Following are the leap years in the given range...\n");
    /*Use of do ... while loop */
    do
    {     /*Body of do loop begins here*/
      /*Testing wheather given year is a leap year or not*/
      if(leapf(current))
      {   /*Body of if true condition begins here*/
          fprintf(stdout,"%10li",current); /* %8i here ensures to print the output
                                          * in at least 8 columns */
          /*Using counter to count the number of columns displayed */
          counter++;
          /*Testing wheather the columns displayed are equal to the specified */
          if(counter==COLS)
          {
             /*If specified columns have been displayed, move to next line */
             printf("\n");
             /*Reset the column counter to 0 */
             counter=0;
          }
      }
      current++;       /*Increment to year*/
    }       /*Body of the do loop ends here */
    while(current<=max); /*Condition of do...while loop is specified here*/
    /*If the above condition is still true, do body will execute once more
      else the control will move to next line*/
    fprintf(stderr,"\nLeap years has been displayed successfully.\n");
    /*Above message will go to monitor - even if output is redirected
      because it is being send to standard error terminal not standard output*/
    return 0; /*returning control back to Operating System */
}