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APPENDIX B
SUGGESTED PLOT55 APPLICATIONS
This appendix contains examples of FORTRAN subroutines that combine various PLOT55 calls to
achieve "higher level" functions. For example, your use of a VT55 might require the display of a large num-
ber of graphs, in which case you can avoid a large number of PLOT55 calls in your program by following
the techniques suggested in this appendix.
Not all of these routines would be needed by every user, and there is rarely any saving in execution speed,
because the routines result in just about the same number of PLOT55 calls as would occur anyway. The
advantage of subroutines is that they allow you to define, debug, and save an entire procedure, which can
then be reused as often as necessary without the risk of new programming errors.
You can try the routines suggested in this appendix by compiling and linking them as you did for PLOT55.
You may find that they can be used as they are shown here or that some additional modifications would
make them more applicable to your needs.
Notice that these subroutines use the four-argument form of PLOT55. The fourth argument is the 16-ele-
ment array 1ST AT, and it is placed in a common area labeled STATUS. The use of such a common status
table allows you to share the same status information between any number of routines. Within each rou-
tine, individual elements of 1ST AT can be examined and changed to control the overall status of the VT55
display. For example, the element ISTAT(8) stores the current graph number; ISTAT(8) equals 0 if Graph
o
is in use and 8 if Graph 1 is in use. The full list of status table elements and their uses is as follows:
ISTAT(l):
ISTAT(2):
ISTAT(3):
ISTAT(4):
ISTAT(5):
ISTAT(6):
ISTAT(7):
ISTAT(8):
ISTAT(9):
ISTAT(10):
ISTAT(l1):
ISTAT(12)-
ISTAT(16):
B.t INITIALIZATION
Logical unit number of terminal.
Event flag number to be used.
X value of origin.
Y value of origin.
Work register (do not change contents!).
Work register.
Graphic status (holds the current total from IENAB).
o
if Graph 0 is in use; 8 if Graph 1.
Graphic mode switch (O=Off, I=On).
Work register for vectors (do not change!).
Character count (RSX
-11
only).
Character output buffer (RSX -11).
In most applications, it is useful to have a routine such as the one shown here that will return the VT55 to
some initial state as preparation for running a new program.
SUBROUTINE INIT
COMMON/ST
ATUS/ISTAT(16)
DATA
ISTAT/16*01
B-1
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