The GDFV2 is an improved and enlarged version of the GDFV1, but the GDFV1 is not directly compatible with the GDFV2. Changes for programmers and end-users are described in the sections 5 and 6 respectively.
Reading the GDFV2 file structure from disk with an old version (older than May-2012) of Gildas is not possible: the file will not be recognized and the following error message will be returned:
E-RIS, File xxx.gdf is neither a GILDAS data frame nor a SIMPLE FITS file
Reading the GDFV1 file structure from disk (in any format, including VAX) is still possible; it is mapped on the fly to a GDFV2 structure in memory. On the other hand, writing GDFV1 is not possible anymore.
For convenience, during a transition phase, some update operations remain possible. Extending a GDFV1 data file, for example (via the DEFINE IMAGE A[n] gdfv1.gdf EXTEND command), is still possible. Updating the extrema is also possible. Similarly, extending a pre-existing GDFV1 UV Table in CLIC is allowed.
These specific facilities are only provided to ease the transition between GDFV1 and GDFV2, and will ultimately be removed from the GILDAS package. The user is thus encouraged to convert its data files to the new format. The simple SIC procedure @ gag_pro:gdf_convert will do this.