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System parameter file   SP100000.

A. Overview

Function:  The system parameter file provides programs with information
about the system resources that are available to AIPS.

Details:  All AIPS programs read this file as one of the first steps of
program execution.  This is a permanent file created at AIPS instal-
lation time either with FILINI or FILAIP or as part of an automatic
installation procedure that is available on a limited number of
computers.  The size needed is one 256 word block, rounded up to one
granule.

Name:  The file name is SP100000.

B. File structure

   The file consists of one 256 word logical record.

  FIELD   TYPE   DESCRIPTION

    1     I*2     Number of disk drives available.
    2     I*2     Number of tape drives available.
    3     I*2     Number of lines per CRT page.
    4     I*2     Number of lines per print page.
    5     I*2     Number of batch queues.
    6     I*2     Plotter no. of X dots per page.
    7     I*2     Plotter no. of Y dots per page.
    8     I*2     Plotter no. of X dots per character.
    9     I*2     Plotter no. of Y dots per character.
   10     I*2     Maximum no. of interactive users.
   11     I*2     Number of words in AP (in 1024 sections).
   12     I*2     Number of TV devices available.
   13     I*2     Number of graphics devices (like TEK 4012) available.
   14-63  I*2(50) Device table (see below).
   64     I*2     No. of users allowed access to TVs.
   65     I*2     No. of users allowed access to graphics devices.
   66     I*2     No. of entries in private catalogs. 0=> public catalog.
   67     I*2     Free
   68     I*2     Free
   69     R*4     No. of dots per mm on printer.
   70     R*4     No. of dots per mm on graphics screen.
   71     R*4(5)  System name or ID (4 characters/floating point).
   REST OF BLOCK  Free

   The device table is used to describe the characteristics of a file
that can be opened on a specific AIPS I/O logical unit number.  The
logical unit numbers run from 1 to 50 and are described by its
corresponding device table value.  The codes for the device table
values are listed below.

  DEVICE TABLE       TYPE OF FILE OPENED ON THE CORRESPONDING LUN
     VALUE
       0             File manager file with FTAB
       1             Fortran device (no FTAB)
       2             Non-file manager with FTAB
       3             Other, no FTAB
       4             television device with FTAB

   If this isn't clear, don't be alarmed.  The device table need not be
changed unless significant alterations or additions to AIPS are made.

C. Routines and commons for reading the system parameter file.

   The subroutine ZDCHIN (called by every program in the initial stages
of execution) will open, read and then close the system parameter file.
The information is then transfered by ZDCHIN to commons DCHCOM and FTABCM
which are found in include file CDCH.INC.

D. Routine for initializing and updating the system parameter file.

   Stand alone program SETPAR allows the AIPS manager to initialize the
system parameter file during AIPS installation or to modify the file
when conditions warrant (for example when another disk is made available).

   SETPAR is an interactive program with prompts.  The first prompt that
appears when SETPAR is run is:

   ENTER: I4  1=INIT, 2=CHANGE VALS, 3=CHG DEVTAB, 4=QUIT

The I4 tells the user that the response should be input in FORTRAN I4
format.

Option 1 (INIT).
   This option is normally chosen during AIPS installation.  SETPAR will
initialize the values in the SP file with the default values but SETPAR
will not create an SP file.  This must be done with program FILINI or
FILAIP.  After initializing the values SETPAR will immediately proceed
to option 2 described below.

Option 2 (CHANGE VALS)
   This option allows the AIPS manager to change the current SP file
values.  When this option is chosen the current values and a descrip-
tion is printed on the CRT.  Then the following prompt is printed.

   ENTER NUMBER TO CHANGE I4  0=PRINT,  -1=RETURN

The "number to change" in the prompt refers to the number on the far
left of the description of the value.  For example if the user wants
to change the number of disks available to AIPS from 2 to 3, then
the user finds the following line on the CRT:

   1  NUMBER OF LARGE DISKS           2

In this case the 1 is the "number to change" and 2 is the current
number of disks.  Thus, the user enters 1 in FORTRAN I4 format.
The next prompt is:

   1  NUMBER OF LARGE DISKS           2

The user then enters a 3 in FORTRAN I4 format.  The program then
reprints the prompt:

   ENTER NUMBER TO CHANGE I4  0=PRINT,  -1=RETURN

At this point, the user can change another value by entering the
proper positive number, or reprint the latest values by entering a
0, or return to the very first prompt (from which the quit command
can be issued) by entering a -1.

Option 3 (CHG DEVTAB)
   This option allows the user to change the device table values
described above.  The details of operation are very similiar to option
2.

Option 4 (QUIT)
   This option will save the latest SP file values and stop the program.

