Multiple Extension FITS files.			August 1997

The MEF interface is a set of routines to manipulate single FITS files
or Multiple Extensions FITS files. This interface complies with the
FITS standard set by the NOST document.

The MEF interface is an IRAF interface intended to be used within an SPP
or Fortran program with the proper IRAF initialization routines.

The user callable routines are:

mef_open (filename, acmode, ofd)

	Integer procedure returning a pointer to the MEF structure.

	'filename'. Pathname to the target FITS filename. Pathname
	            consist of
	
	     ldir$rootname.extn[group]

	     ldir:  Logical directory
	     root:  Rootname of the filename
	     extn:  (Optional) FITS filename extension.
	     group: (Optional) The FITS extension number. Zero correspond
		    to the the Primary Header Unit, 1 to the first 
		    extension on so on. If you specify group, the '[]' are
		    required.
		

	'acmode'. Access mode of the target file. It could READ_ONLY,
	          READ_WRITE, NEW_FILE or APPEND.

	'ofd'. Not used at the moment. Reserve for future use.

	mef = mef_open (filename, acmode, ofd|hsize)

	The MEF structure pointed by 'mef' consists of the following
	elements:


       	MEF_FD           # File descriptor
       	MEF_HOFF         # Header offset in chars
       	MEF_ACMODE       # Access mode
       	MEF_ENUMBER      # Absolute extension number
       	MEF_EXTVER       # EXTVER keyword value
       	MEF_CGROUP       # Current group read
       	MEF_HSIZE        # Header size
       	MEF_HDRP         # Header area pointer
        MEF_POFF         # Offset to pixel area in chars
       	MEF_NDIM         # Unit dimensionality
       	MEF_NAXIS        # Lenght of each exis
       	MEF_BITPIX     	 # Value of BITPIX
       	MEF_EXTTYPE      # XTENSION keyword value 
       	MEF_FNAME        # Filename
       	MEF_OBJECT       # OBJECT keyword value
       	MEF_EXTNAME      # EXTNAME keyword value

mef_close
	mef_close (mef)

	Free the memory allocated by mef_open and close the target
	FITS file.

mef_query
	mef_query (filename, ext_type, datatype, object)  
	
	Mefopen already does this, the difference would be for example
	that mef_query would just returns  its argument values. No need to
	open and close.

	Another approach is to open the file, and mef_query would just 
	return and value per request, for example

mef_stati
	val = mef_stati (mef, "EXT_TYPE")

	to get the value of a mef descriptor element.

mef_delete
	Make a temporary copy of file and copy the rest of the
	extensions. Delete the old one.
	
	mef_delete (mef)

mef_rename
	Considering that an extension is a portion of a file, renaming
	would be limited to change the names of the EXTNAME and/or EXTVER
	values. No extractions to a different filename would be allowed.

	mef_rename (in_mef, oldname, new_name, unique(YES|NO))

	Does the new_name need to be unique?

mef_extract
	Make a copy of an extension into a new or existent file.

	mef_extract (file.fits[4], output_file, new|append)

mef_insert
	Insert an extension after an existent one. Again a temporary file
	would be necessary to preserve the integrity of the target file.

	mef_insert (in_mef, out_mef, out_extn)

mef_overwrite
	This would equivalent to delete an insert but only one temporary
	file would be necessary.

	mef_overwrite (in_mef, out_mef, out_extn)

gethdkw 
	Get keyword value, e.g.

	real = gethdkwr (mef, keyword) 

	val = gethdkw[bsird] (mef, keyword)
	call gethdkwstring (mef, keyword, buf, max_size)

puthdkw
	Put keyword value (new or update value), e.g.

	call puthdkw[bsird] (mef, keyword, value, comment)
	call puthdkwstring (mef, keyword, value, max_size, comment)