The file ncbi.tar.Z is an L-Z compressed UNIX tar archive that contains all of the files splayed beneath the "explode" subdirectory. FTP this file to your local machine in binary mode, uncompress it, then untar it. The ncbi.tar file is the same file, just not compressed. VMS compress, uncompress, and tar utilities are posted on this machine in the /toolbox/vms_util directory. The coretool subdirectory contains pre-release versions of some NCBI standard header files. Headers for several computer software/hardware platforms are predefined there. This is a skeletal library with no .c files; its sole purpose is to make it easier to build the BLAST application programs. The complete ncbi library is posted beneath the /toolbox/ncbi_tool directory, but it is presently unnecessary for building the BLAST application programs. INSTALLATION Identify the ncbilcl.* file appropriate for your platform in the "coretool" directory and make a copy of it in the "include" directory, giving the copy the new name of ncbilcl.h. If none of the existing ncbilcl.* files are appropriate, create one yourself using the others as models. The ncbilcl.sun and ncbilcl.sgi files may be good starting points. If one is interested in reading more about how to write portable C software, there are at least two books currently on the market; their mention here does not constitute endorsement. "Portable C Software," by Mark R. Horton (1990), Prentice Hall, Englewood Cliffs, New Jersey, ISBN 0-13-868050-7. "Portable C," by Henry Rabinowitz and Chaim Schaap (1990), Prentice Hall, Englewood Cliffs, New Jersey, ISBN 0-13-685967-4.