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PHI - IMPLEMENTATION DETAILS
   1 Compilation
   2 Loading and saving
   3 Files required
   4 Usage logging
   5 Monitor mods to implement PHI command
   6 Special facilities

PHI - IMPLEMENTATION DETAILS
----------------------------


   1 Compilation
     -----------

   To compile the program leaving all assembly parameters as defaults just type
   .COMP PHI
   This will produce a version which is suitable for using to examine individual
   .PHI files, and which will also form the basis of a PHI Help System.
   Note that the universal files MACS.UNV and UUOSYM.UNV are required for
   compilation.
   PHI is written in 'structured Macro' using the structuring macros defined
   in MACS.UNV. Because of this it is not advisable to obtain a CREF listing
   of the program as it can be rather confusing to read.
   
   To compile PHI altering any of the assembly parameters:
   .R MACRO
   PHI=TTY:,DSK:PHI
   parameter=value
   parameter=value
   .....
   ^Z
   ^Z
   ^Z
   
   Some of the assembly parameters that may need to be changed are as follows:
   
   (i) SUBJ0 is the name (in SIXBIT) of the top level file when PHI is being
       used as the basis of a Help System. This is the file (with extension
       .PHI) that will be read in when no subject name is typed when running
       PHI. The default value is SIXBIT/0/, i.e. a file DOC:0.PHI is expected.
       If you are not using PHI as the basis of a Help System then it is
       best to set SUBJ0=0 (i.e. SIXBIT/ /).
   
   (ii) LOG is a parameter which determines whether the special logging
       facility (based on IPCF messages) is to be used. Its default value
       is 0 which means that the facility is not required. It should
       be set to 1 if the facility is required. For further details see
       the section on 'Usage logging'.
   
   For details of the other assembly parameters see the source code, but
   it is unlikely that these will need to be changed.


   2 Loading and saving
     ------------------

   If the logging facility is not being used just type
   .LOAD PHI
   .SSAVE
   
   If the logging facilty is required however, it will be necessary to
   link in further routines from the file IPSUBS.REL. To do this:
   .R LINK
   *PHI
   *IPSUBS
   */GO
   .SSAVE

   3 Files required
     --------------

   PHI can be used to read .PHI files from any area. Any files that are
   to be generally available should be put onto DOC:. For details of how
   PHI looks for files given a certain subject name, see the full documentation
   file, PHI.PHI.
   If PHI is to form the basis of an online Help System, a file DOC:0.PHI
   should be set up, which contains 'indirect file references' to
   all the other DOC:*.PHI and HLP:*.HLP files available. This file will
   itself have a tree structure and this structure should be carefully
   designed to reflect the logical structure of the whole Help System
   information. An example of a 0.PHI file is included with the program tape.


   4 Usage logging
     -------------

   There is a special facilty to log the usage of PHI based on sending
   IPCF messages to a program 'IPCFR' which will be running detached.
   If the assembly switch LOG has been set to 1 on compilation, then
   when PHI is used it will first see if the program 'IPCFR' is running
   (by sending a message to SYSINF). If the program
   is running, then PHI will send messages to IPCFR containing details
   of subject name typed, all commands typed, and all files read in.
   IPCFR will then write these to a logging file IPCFR.OUT on the
   area in which it is running.
   In this way a check can be made of which subjects users are requesting
   information on, and which PHI commands they are using.
   Note that including logging facilities in PHI may slightly slow down
   the response time at the start of each PHI run, as the program has to
   send a message to SYSINF and wait for a reply.
   
   The program IPCFR is included with the program tape. To compile
   and link it:
   .COMP IPCFR
   .R LINK
   *IPCFR
   *IPSUBS
   */GO
   .SAVE


   5 Monitor mods to implement PHI command
     -------------------------------------

   To create a command 'PHI' in the monitor it is necessary to insert the following
   line into the command table in COMCON:
         C      PHI,RUNAMC,RUNFLG


   6 Special facilities
     ------------------

   The following PHI commands are not described in the user documentation
   as they were intended mainly for testing the program:
     -  after subject name switches on printing of messages every time the

        core taken by the program is changed.
     += defines a sub-tree with the current node as its root within which +
        and +> commands will operate.
     +> move to next root node (i.e. next file)
   
   Global printing.
   Normally when doing a P command, indirect file references in virtual
   nodes are not resolved, i.e. the files are not read in, instead just the
   file spec is printed as it stands.
   However by recompiling the program and setting the assembly parameter
   PVAL, PHI can be made to print out not only the current file but also
   files which are linked through indirect file references.
   Each indirect file spec can be followed by /Pn where n is an integer
   0, 1, 2, etc. The default if /Pn does not appear is n=0. An indirect file
   will then be printed if its P value is not greater than PVAL.
   Thus very long files could have higher P values enabling these to be
   ommitted from a global printout. e.g. if PVAL=1 on compilation then
   only nodes with a P value of 0 or 1 will be printed.
   This facilty can be used to obtain a printout of the whole
   Help System (and so is obviously too dangerous to make generally
   available to users as it can result in vast quantities of output).