Identifier     write2hist

 Purpose        write a comment into the history tag of a given
                IA/ISAP structure

 Synopsis       write2hist, struc ,co [,/no_ts] [,stat=stat]

 Arguments      Name      I/O  Type      Description
                -----------------------------------------------------
                struc     I/O  struct    IA structure containing a history tag
                                         (e.g. AAR or Cal-G file)
                co         I   string    string to be written as a comment
                                         into the history tag
                no_ts      I   switch    don't write a time stamp
                stat      I/O  int       error status, 0 if ok, 1 if fatal
                
 Returns        ---

 Description    The default entry to the history tag is a time stamp followed 
                by the comment entry. The time stamp (in the default IDL 
                systime format) will always be written except if the keyword 
                /no_ts is set. The format of the entries looks like:
                
                HISTORY = 'CO: informative string'

                An informative string that is longer than 80-8-2-6=64
                characters will be broken and continued in the next line. This
                continuation line will NOT contain the two character code CO.
                The supplied strings will be filled up to 64(68) characters
                to maintain a clean 80-character history layout.

                When the history string gets too long (more than 32767
                characters) the dimension of the history string array will be
                increased by one.

 Comment        see also update_history.pro
                
 Example           write2hist, out, 'Now it works!',/no_ts

 Dependencies   CALLS: add_history_string, sap_error
                CALLED FROM: IA

 Category       ISAP

 Filename       write2hist.pro

 Dependencies   add_history_string.pro

 Author         E. Sturm (--> ES)

 Version        1.1

 History        0.1   2-11-95   ES    
                1.0   30-11-95  ES  V1 delivery
                1.1   10-07-96  ES  stat added
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
Copyright (C) 1995, Max-Planck-Institut fuer extraterrestrische Physik (MPE);
                    Garching, Germany                                       ;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;