1 File_Format

    GILDAS is based on a virtual memory  system  which  recognises  a unique
    file   format.    This   format  may  however  be  used  for storing two
    somewhat different kinds of data :

      1. IMAGES :
        Images are regularly sampled 2-d,  3-d  or  4-d  data which  require
        conversion formula for the coordinates along each axis.  Data values
        may be Integer, Real  or  Double   precision,  but  most  algorithms
        support only REAL images.

      2. TABLES :
        Tables are  ensembles  of  columns   strictly   equivalent  to   the
        formatted   files   used   by  GreG  as  input for the X,Y,Z buffers
        (indeed GreG is also able to read  and  write  Tables).   The   only
        difference   is  that they are unformatted, and hence access time is
        typically 50  times  faster...   The  number  of lines   is   fixed,
        but  the  number  of columns may be extended indefinitely.  In fact,
        a table may be consider as a 2-D  image (and   vice-versa   if   you
        want)  but  does  not require "axis" information...


    Tables and Images may be produced by other softwares (mainly   CLASS  if
    one   considers   that   GreG   is  a  subset  of  GRAPHIC),  and  fully
    manipulated  by  the  GILDAS  environnement.   They  can  be   used   in
    mathematical formulae in SIC monitor.
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