*+
*  Name:
*     IMG_ECB

*  Purpose:
*     Define the IMG_ Extension Control Block.

*  Language:
*     Starlink Fortran 77

*  Type of Module:
*     Fortran include file.

*  Description:
*     This file defines Fortran common blocks constituting the IMG_
*     system Extension Control Block (ECB). This holds details of
*     which extension are currently available in an NDF. The NDF slot
*     number is the same as that used in the Parameter Control Block.

*  Prior Requirements:
*     The files IMG_CONST NDF_PAR and DAT_PAR must be included before
*     this file, in order to define necessary constants.

*  Authors:
*     PDRAPER: Peter Draper (STARLINK - Durham University)
*     {enter_new_authors_here}

*  History:
*     19-JUL-1994 (PDRAPER):
*        Original version.
*     22-AUG-1994 (PDRAPER):
*        Removed FITS modification check array.
*     2-SEP-1994 (PDRAPER):
*        Added space for storing pointers to extension locator stacks.
*     15-NOV-1994 (PDRAPER):
*        Removed ECB_XREAD variable. Readonly access is no longer
*        checked.
*     {enter_further_changes_here}

*  Bugs:
*     {note_any_bugs_here}

*-

*  Global Variables:
      CHARACTER * ( NDF__SZXNM ) ECB_XNAME( IMG__MXPAR, IMG__MXEXT )
                                 ! Extension names
      CHARACTER * ( DAT__SZLOC ) ECB_XLOC( IMG__MXPAR, IMG__MXEXT )
                                 ! Extension names
      INTEGER ECB_FTSP( IMG__MXPAR )  ! Pointers to mapped  FITS block
      INTEGER ECB_FTSN( IMG__MXPAR )  ! Number of entries in FITS block
      INTEGER ECB_XPSTK( IMG__MXPAR, IMG__MXEXT ) ! Pointers to
                                 ! extension locator stacks
      INTEGER ECB_XNSTK( IMG__MXPAR, IMG__MXEXT ) ! Number of locator in
                                 ! extension stacks.
      INTEGER ECB_XNLEN( IMG__MXPAR, IMG__MXEXT ) ! Length of the
                                 ! (hds_)trace of the extension locator.

      COMMON /IMG1_ECB1/ ECB_XNAME, ECB_XLOC
      COMMON /IMG1_ECB2/ ECB_FTSP, ECB_FTSN, ECB_XPSTK, ECB_XNSTK,
     :                   ECB_XNLEN

*.
* $Id: img_ecb,v 1.1 1998/06/03 13:15:25 pdraper Exp $
