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0.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.~
1.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~
1.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.~
1.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~
1.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~
1.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).~