Identifier     sap

 Purpose        prepare ISAP history handling

 Synopsis       sap, logfile=logfile

 Arguments      Name      I/O  Type      Description
                -----------------------------------------------------
                logfile    I   keyword   the name of the session log file
                                         default:'sap_session.log'
                
 Returns        ---

 Description    This routine initiates the ISAP history handling. It
                shall be called at the beginning of an ISAP session which will
                be automatically done when starting IA (or the GUI).
                An eventual user supplied journal file is closed and the 
                standard ISAP journal file (a temporary scratch file) is 
                opend. A session log file for the whole IA/ISAP session is 
                opened as well.
                This routine is intended to be used in combination
                with squit.pro at the end of the session and with a call to
                update_history in appropriate IA and in ISAP (shell) routines.
                At the end of a session the user will have 
                   1) all informations about an IDL session up to the start of 
                      IA/ISAP in his own journal file (if such a file was
                      provided), 
                   2) the calls of IA/ISAP routines, i.e. the command lines,
                      in the history tag of the output structures, and
                   3) a session log file of the complete IA/ISAP session in a 
                      specified file.

 Comment        The GUI history handling will be different and will be
                developed later.
                The definition of !SAP_GUI ( set to 0) should also be added 
                to the IA startup file.

 Example        ---

 Dependencies   CALLS: sap_keyword_set
                CALLED FROM: GUI, IA at the beginning of the session (planned)

 Category       ISAP

 Filename       sap.pro

 Author         E. Sturm (--> ES)

 Version        1.0

 History        0.1   15-10-95  ES  
                0.2   24-10-95  ES       added keyword logfile, removed
                                         prompt for filename
                1.0   30-11-95  ES       V1 delivery
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Copyright (C) 1995, Max-Planck-Institut fuer extraterrestrische Physik (MPE);
                    Garching, Germany                                       ;
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