To install SCAN:
---------------

(We're assuming that the SCAN components are in the current directory...)

Add the help to the system help library. The new element will appear as
DIRECTORY_SCAN in the help list...

$ LIBR/INSERT SYS$HELP:HELPLIB SCAN.HLP/HELP

Next, compile the TPU section file. This will create a file called
SYS$LIBRARY:DIRECTORY_SCAN.TPU$SECTION

$ EDIT/TPU/NOSECTION/COMMAND=SCAN.TPU

Make it accessable by everyone by entering

$ SET FILE SYS$LIBRARY:DIRECTORY_SCAN.*/PRO=W:RE

Compile and install the SCAN external routines.

$ BASIC SCAN_EXTERNAL
$ LINK/SHARE SCAN_EXTERNAL/OPT

Place in SYS$LIBRARY the file SCAN_EXTERNAL.EXE with W:RE protection.

Finally, add to the system start files the command 

$ DEFINE/SYSTEM TPU$CALLUSER SYS$LIBRARY:SCAN_EXTERNAL.EXE

For using SCAN interactively, type HELP DIRECTORY_SCAN INSTALL

That's all there is to it. If for some reason, you do not like calling
it DIRECTORY_SCAN, you can edit the help and TPU source files to make it
whatever you want.