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 the tar archive to your local machine in binary mode, uncompress it, then untar it. VMS compress, uncompress, and tar utilities are posted on this machine in the /toolbox/vms_util directory. The corelib subdirectory contains versions of some platform-specific header files. Headers for several computer software/hardware platforms are provided. This archive constitutes a skeletal library with no .c files; its sole purpose is for building the BLAST application programs. The complete ncbi library is posted beneath the /toolbox/ncbi_tools directory, but it is presently unnecessary for building the BLAST application programs and may actually be an incompatible version. INSTALLATION To unpack the compressed tar archive, the following two commands may be executed. The archive will be unpacked in a subdirectory named "ncbi". uncompress ncbi.tar tar xf ncbi.tar Alternatively, a single command pipeline may be used to unpack the archive: zcat ncbi.tar | tar xf - Identify the ncbilcl.??? file appropriate for your platform in the "corelib" 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 multiprocessing is available and you wish it to be employed on your computer system (assuming multiprocessing is supported on your platform by the BLAST software), make sure the MPROC_AVAIL macro is #defined at the beginning of ncbilcl.h. By default, this macro is commented-out. 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.