Xtal Year 2000 compliancy isssues.

Xtal3.6 is largely impervious to Y2K compliancy issues, but unfortunately we cannot guarantee or warranty 100% compliancy, owing to different hardware, operating systems and link libraries on target computers, over which we have no control.

Xtal makes no use of time stamps to calculate, compare or sequence data, nor yet to control reading or writing of files on the filesystem. All Xtal file accesses are sequential, in the sense that files will be read, written or overwritten solely in the sequence by which the user, invokes the various Xtal3.6 subprograms. Consequently any responsibility for loss of data whilst using Xtal3.6 lies purely with the end user!

HOWEVER Xtal3.6 does make use of the local system time, typically through standard Fortran77 library routines - such as ETIME and FDATE. The times and dates obtained from these functions are solely used to provide users with information about file creation/modification dates and program calculation times.

Versions of Xtal compiled for the following operating systems use ETIME and FDATE from the F77 library.

      OS                                              COMPLIANCY
  Compaq/DEC ALPHA Tru64/DIGITAL UNIX 4.0D or greater   YES >=4.0D        
  Compaq/DEC ALPHA OpenVMS7.1 or greater                YES >=6.5    
  DEC   ULTRIX4.4                                       NO-NEVER!       
  SGI   Indy  Irix5.2  (IP22)   R4000                   NO-NEVER!     
  SGI   O2    Irix6.3  (IP32)   R5000                   NO  <6.5   
  Microsoft Win32 95/98/NT (Intel)                      YES >D.V.F.5.0    
  SUN   SPARCSTATION 2  SunOS 4.1.1                     NO-NEVER

No warranty can or will be provided by us pertaining to the Y2K compliance of these external library functions, those being the responsibility of third party vendors. In particular the Xtal3.6 version built for COMPAQ (nee DEC) ULTRIX 4.4 (RISC) was created with static linkage to the f77 libraries, which according to COMPAQ: (see http://www.digital.com/fortran/y2k.html)

"  The following minimum versions of Compaq Fortran products are warrantied as
              "Year 2000 Ready":

                  DIGITAL Fortran V4.0 for DIGITAL UNIX (Tru64 UNIX) Systems 
                  DIGITAL Fortran V7.0 for OpenVMS Alpha Systems 
                  DIGITAL Fortran 77 V6.5 for OpenVMS VAX Systems 
                  DIGITAL Visual Fortran V5.0 

   The following product is retired and will not be made Year 2000 Ready:

                  DEC FORTRAN FOR ULTRIX RISC Systems "

Consequently the ULTRIX 4.4 (RISC) version will NEVER be fully Y2K compliant. On the other hand the Microsoft Win32 (INTEL) version of Xtal3.6 which was compiled with DIGITAL Visual Fortran V5.0 and should be Y2K compliant, provided it is run on an intel machine with a BIOS and OS that are also Y2K compliant.

Additionally Silicon Graphics provide no upgrade mechanism for making any pre-irix5.3 operating systems Y2K compliant. If an end user has explicitly requested software for irix5.2 it is assumed that they are prepared for the consequences! Note that the irix5.2 version of Xtal was linked against shared libraries so if the enduser has upgraded to a Y2K compliant OS and library set, it is possible that their local F77 libraries will be Y2K compliant and, excluding library incompatabilities, their irix5.2 Xtal version may well continue to work compliantly.

Versions of Xtal compiled for the following operating systems emulate F77 ETIME and FDATE by calls to the POSIX standard C libraries.

      OS                                                         COMPLIANCY
  Slackware (.tgz) GNU/Linux ix86 libc5 based only (pre-libc 2.0)  YES
  Debian    (.deb) GNU/Linux ix86 Slink and Potato (libc6 ...)     YES
  Redhat    (.rpm) GNU/Linux ix86 (5.x)                            YES
  IBM   AIX 4.2.1   RS6000                                         MAYBE??

The slackware linux version was developed using G77 and GCC, both of which interface to the standard UNIX 4 digit year routines in libc5. The gcc version which was used to compile the ETIME and FDATE simulation code has passed Y2K compliancy tests. (see http://www.gnu.org/software/year2000-list.html)

The IBM version was compiled with static libraries. Presumably since all versions of AIX >3.2.5 can be made compliant, we could expect that the libc C library statically linked to the IBM version of Xtal3.6 will be Y2K compliant. (see http://www.software.ibm.com/year2000/papers/aixy2k.html)

That being stated, it is re-emphasised that as far as the operation of Xtal3.6 is concerned, the only effect of such hardware, operating-system or external-library non compliance will be incorrect date and time stamps in output listings and archive files. This potentially incorrect date information is provided purely for users convenience and can have no effect on the inner workings of the Xtal3.6 system of crystallographic software, which in fact should remain useful well into the 21st century - or until your next upgrade (which ever comes first).

Xtal3.6 continues to record the year as a 2 digit number in such listings.