Example

The following C programming example shows a practical application
of the DECdts API programming routines. The program performs the
following actions:

   o  Prompts the user to enter time coordinates.

   o  Stores those coordinates in a tm structure.

   o  Converts the tm structure to a utc structure.

   o  Determines which event occurred first.

   o  Determines if Event 1 may have caused Event 2 by comparing the
      intervals.

   o  Prints out the utc structure in ISO text format.

   #include <time.h>   /* time data structures                   */
   #include <utc.h>    /* utc structure definitions              */

   void ReadTime();
   void PrintTime();

   /*
    * This program requests user input about events, then prints out
    * information about those events.
    */

   main()
   {
       struct utc event1,event2;
       enum utc_cmptype relation;

       /*
        * Read in the two events.
        */

       ReadTime(&event1);
       ReadTime(&event2);

       /*
        * Print out the two events.
        */

       printf("The first event is : ");
       PrintTime(&event1);
       printf("\nThe second event is : ");
       PrintTime(&event2);
       printf("\n");

       /*
        * Determine which event occurred first.
        */
       if (utc_cmpmidtime(&relation,&event1,&event2))
           exit(1);

       switch( relation )
       {
           case utc_lessThan:
           printf("comparing midpoints: Event1 < Event2\n");
           break;
           case utc_greaterThan:
           printf("comparing midpoints: Event1 > Event2\n");
           break;
           case utc_equalTo:
           printf("comparing midpoints: Event1 == Event2\n");
           break;
           default:
           exit(1);
           break;
       }

       /*
        * Could Event 1 have caused Event 2?  Compare the intervals.
        */

       if (utc_cmpintervaltime(&relation,&event1,&event2))
           exit(1);

       switch( relation )
       {
           case utc_lessThan:
           printf("comparing intervals: Event1 < Event2\n");
           break;
           case utc_greaterThan:
           printf("comparing intervals: Event1 > Event2\n");
           break;
           case utc_equalTo:
           printf("comparing intervals: Event1 == Event2\n");
           break;
           case utc_indeterminate:
           printf("comparing intervals: Event1 ? Event2\n");
           default:
           exit(1);
           break;
       }

   }

   /*
    * Print out a utc structure in ISO text format.
    */

   void PrintTime(utcTime)
   struct utc *utcTime;
   {

       char   string[50];

       /*
        * Break up the time string.
        */

       if (utc_ascgmtime(string,      /* Out: Converted time    */
                         50,          /* In:  String length     */
                         utcTime))    /* In:  Time to convert   */
           exit(1);
       printf("%s\n",string);
   }

   /*
    * Prompt the user to enter time coordinates.  Store the
    * coordinates in a tm structure and then convert the
    * tm structure to a utc structure.
    */

   void ReadTime(utcTime)
   struct utc *utcTime;
   {
   struct tm tmTime,tmInacc;

       (void)memset((void *)&tmTime,  0,sizeof(tmTime));
       (void)memset((void *)&tmInacc, 0,sizeof(tmInacc));
       (void)printf("Year? ");
       (void)scanf("%d",&tmTime.tm_year);
       tmTime.tm_year -= 1900;
       (void)printf("Month? ");
       (void)scanf("%d",&tmTime.tm_mon);
       tmTime.tm_mon -= 1;
       (void)printf("Day? ");
       (void)scanf("%d",&tmTime.tm_mday);
       (void)printf("Hour? ");
       (void)scanf("%d",&tmTime.tm_hour);
       (void)printf("Minute? ");
       (void)scanf("%d",&tmTime.tm_min);
       (void)printf("Inacc Secs? ");
       (void)scanf("%d",&tmInacc.tm_sec);

       if (utc_mkanytime(utcTime,
                         &tmTime,
                         (long)0,
                         &tmInacc,
                         (long)0,
                         (long)0))
           exit(1);

   }

   Assume the preceding program is named compare_events.c. To
   compile and link the program on a DECnet-Plus for OpenVMS system,
   enter the following command:

   $ cc compare_events.c/output=compare_events.obj
   $ link compare_events.obj, sys$input:/options<Return>
   sys$library:dtss$shr.exe/share<Ctrl-z>
   $