.ps 60 80
.rm 78
.p 0 1 4
.noj
.ap
.ch USING#DIGS#ON#THE#VAX#CLUSTER
.hl 1 INTRODUCTION
VAX  DIGS  is  an  implementation  of  the  Fermilab  Device
Independent  Graphics  System  (DIGS)  for the VAX-11 series
computer under VMS.
Post  Processors
are  available  which  can  produce output from this DIGF on
4010  type  terminals or PRINTRONIX  printers.
.hl 2 Setup
.s 1
The following logical names are defined by the LIB:[LIB.DIGS]SETUP 
procedure, in addition to the PRINTPP, PREVU, and PLOT symbols.
.s 1
.nofill
DIGS__EXE     - Directory containing PRINTPP, PREVU procedures
DIGS__LIBRARY - Directory containing GRALIB library
DIGS__PRINT   - Default Printronix plotting device
.f
.hl 1 LINKING#AND#EXECUTION
 To include GRALIB in a LINK, follow this example:
.s 1
$ LINK file1,file2,...,filen,DIGS__LIBRARY:GRALIB.OLB/LIBRARY
 The COLOR subroutine is supported  by
VAX  DIGS,
either to DIGF's or to the Envision
terminal.
 If  no  special  assignment  is
made,  any DIGF produced will be named DIGF.DAT on the
current default area.  (The  current  default  area  may  be
determined with the command: $ SHOW DEFAULT )
 The name of the DIGF may be changed by defining a  file
name  as  in the following example:
.s 1
$ DEFINE DIGF  filename
.hl 1 DISPLAYING AND PLOTTING A DIGF
The mechanism for viewing the graphics described in DIGF files is the
Post Processor (PP).  A PP reads the data in the DIGF, and a command
stream either from an interactive terminal or from a Device
Independent Graphics Indirect Commands file (DIGIC).  It responds to
the command stream either by plotting the data directly on the target
device, or by producing a device-specific file which is routed to the
device for output at the end of PP execution.
 Invoking PP's - PRINTPP may be invoked by typing PRINTPP after having
defined that symbol with LIB:[LIB.DIGS]SETUP.COM.
 The specification of
DIGF  files  for VAX PP's is as described above for programs
linked using GRALIB.  In addition, the  first  parameter  on
the command line that executes the PP can be the name of the
desired DIGF.   This  parameter  overrides  the  default  of
DIGF.DAT.
 If  no  special
assignment is made, a PP will open a file named DIGIC.CMD on
the current default area.
The name of the DIGIC may be specified by defining  a  file
name  as  in the following example:
.s 1
$ DEFINE  DIGIC  filename
 In addition, the second parameter on the command  line  that executes 
the PP can be the name of the desired DIGIC.  This parameter overrides 
the  default  of  DIGIC.CMD  and   any previous  assignment  of  the
DIGIC logical name for the duration of that execution of the PP. 
 If it is desired to execute the DIGIC file 
immediately, PRINTPP
allows the user to specify GO as the third
parameter. If this is not done, the PP expects that commands will be
entered from the keyboard interactively. This is the recommended manner of
entering commands to PP's that will be executed in a command procedure either
interactively or via BATCH. It is recommended that the last instruction in the
DIGIC be QUIT.
 Command parameters may be delimited by a comma or a single space.  Two
spaces  or two commas in a row are equivalent to a zero parameter.
.s 1
  Printronix PP
.s 1
The PRINTPP procedure produces graphis output for the 
Printronix lineprinter.
PRINTPP expects that the symbol PLOT be defined, typically by placement
of @LIB:[LIB.DIGS]SETUP in the user's
LOGIN.COM file. The recommended definition of PLOT is:
.s 1
$ PLOT :== PRINT/QUEUE=DIGS__PRINT:/NOFEED/NOFLAG/DELETE
 The /DELETE parameter is optional.
The queue name for any standard Printronix graphics
printer could be substituted if desired.
 PRINTPP produces a file named SYS$LOGIN:PXOUT.GRA. This file contains the
characters needed to produce the requested plots on a Printronix printer. These
files can be quite large. Careful attention to their management is suggested.
 PRINTPP rasterizes an area 13.0 inches by 17.0 inches. It does not issue a
formfeed between plots.
 PRINTPP can be instructed to rasterize any area up to 13.0 inches by 17.0
inches. It may optionally skip to top of form between plots. It may optionally
queue the output to the printer specified in the PLOT symbol on exit.
If no additional parameters are included when the PRINTPP command is entered,
PRINTPP will prompt the user for the desired data. As with all VAX PP's, all
input must be in UPPERCASE.
 Parameters for PRINTPP may be entered via logical names as in example below:
.s 1
.nofill
$ DEFINE DIGS__XMAX number
$ DEFINE DIGS__YMAX number
$ DEFINE DIGS__FEED (Y / N)
$ DEFINE DIGS__QUEUE (Y / N)
.f
 The command line for PRINTPP looks like:
.s 1
$ PRINTPP P1 P2 P3 P4 P5 P6 P7
.s 1
 P1 - DIGF specification.
 P2 - DIGIC specification.
 P3 - GO if DIGIC is to be executed immediately,
else blank or "".
 P4 - XMAX, real number between 0.0 and 13.0, number of
inches to be rasterized in the X direction.
 P5 - YMAX, Real number between 0.0 and 17.0, number of
inches to be rasterized in the Y direction.
 P6 - FEED, either Y or N, If Y, then PRINTPP will
insert a formfeed in the plot after each DEINIT
call (usually after each PLOT).
 P7 - QUEUE, either Y or N, If Y, then PRINTPP will
automatically execute the symbol PLOT at end of execution to
queue the output file to the printer.  If N, PRINTPP will type
out the name and version number of the created file prior to end
of execution.
 In addition to the above, PRINTPP can also be instructed not to produce a
DIGS-style banner page by this definition:
.s 1
$ DEFINE DIGS__BANNER N
 If this logical is not defined, PRINTPP will produce a banner by default.
.s 1
  TEK 4010 PP
.s 1
Except as noted above, PREVU conforms to both SP-12 and J-01.
 The command line for PREVU looks like:
.s 1
$ PREVU P1 P2 P3
.s 1
 P1 - DIGF specification.
 P2 - DIGIC specification.
.s 1
PREVU produces color output for Envison terminals.  The use of 4010
hardware characters requires that the terminal be in GRAPH MODE. For further
information on setting up this device , see the "Models 220 and 230 Color
Graphics Terminals Reference Manual", HN-0053.
.s 1
.hl 1 DIGS EXAMPLE
The following example program illustrate the basic use of DIGS:
.nofill

      PROGRAM SPHERE            !DRAW PICTURE OF SPHERE
C**
C** AUTHOR: A. KRZYWDZINSKI
C**
C** LIBRARY OF VARIABLES:
C**
C**  A        COEFFICIENT( (X-XOR)**2/A/A+(Y-YOR)**2/B/B=1)
C**  ALFA     ANGLE IN RADIANS
C**  B        COEFFICIENT(SEE VARIABLE A)
C**  DA       CONSTANT (INCREMENT OF A)
C**  DALFA    CONSTANT (INCREMENT OF ALFA)
C**  DOD      WHAT SHOULD BE ADDED TO Y
C**  DX       INCREMENT OF X VALUE
C**  DY       -----""----- Y --"--
C**  I,J      ARGUMENTS OF DOLOOPS
C**  PI       VALUE OF PI
C**  R        VALUE OF THE RADIUS
C**  X,Y      X AND Y AXIS
C**  XOR,YOR  STARTING POINTS FOR PLOT
C**
C
C CALL PLTSIZ TO SET SIZE OF PLOT PRIOR TO INITDV
C
      CALL PLTSIZ(11.,8.5)
C
C CALL INITDV TO INITIALIZE THE DIGF
C     (SINCE THE NDEV PARAMETER = 0)
C
      CALL INITDV(0,0)
      R=3.
      PI=ACOS(-1.)
      DALFA=PI/26.
      ALFA=DALFA
      XOR=5.5
      YOR=4.25
C
C USE PLOTTO TO PLOT A BORDER AROUND THE PLOT
C
      CALL PLOTTO(0.,0.,3)
      CALL PLOTTO(11.,0.,2)
      CALL PLOTTO(11.,8.5,2)
      CALL PLOTTO(0.,8.5,2)
      CALL PLOTTO(0.,0.,2)
C
C NOW BEGIN PLOTTING THE SPHERE - SPHERE MADE UP OF ELIPSES
C
C PLOTIF IS USED TO PLACE THE LINE SEGMENTS WHICH MAKE UP
C THE DESCRIBED ELIPSES INTO THE DIGF
C
      DO 1 I=1,26
      X=XOR-R*SIN(ALFA)
      DOD=R*COS(ALFA)
      Y=YOR+DOD
      CALL PLOTIF(X,Y,3)
      A=XOR-X
      B=A*.25
      DX=A/38.
      DO 2 J=1,152
      IF(J-76)3,3,4
3     X=X+DX
      Y=F(XOR,YOR,X,A,B,1.)+DOD
      CALL PLOTIF(X,Y,2)
      GO TO 2
4     X=X-DX
      Y=F(XOR,YOR,X,A,B,-1.)+DOD
      CALL PLOTIF(X,Y,2)
2     CONTINUE
1     ALFA=ALFA+DALFA
      B=3.
      DY=3./38.
      A=0.
      DA=3./7.
      DO 5 I=1,8
      X=XOR
      Y=YOR+3.
      CALL PLOTIF(X,Y,3)
      DO 6 J=1,152
      IF(J-76)7,7,8
7     Y=Y-DY
      X=F(YOR,XOR,Y,B,A,1.)
      CALL PLOTIF(X,Y,2)
      GO TO 6
8     Y=Y+DY
      X=F(YOR,XOR,Y,B,A,-1.)
      CALL PLOTIF(X,Y,2)
6     CONTINUE
5     A=A+DA
C
C NOW WE ARE ALL DONE WITH THE PLOT AND USE DEINIT TO CLOSE
C THE DIGF GRACEFULLY...
C
      CALL DEINIT
      CALL EXIT
      END
C
      FUNCTION F(XOR,YOR,X,A,B,W)
      IF(A.EQ.0.)GO TO 1
      F=W*B*SQRT(ABS(1.-(X-XOR)**2./A/A))+YOR
      RETURN
1     F=0.
      RETURN
      END
.f
       The above program is compiled and linked as follows:
.s 1
.nofill
_$!    Compile the program
$ FORTRAN SPHERE
_$!    Link the object file with GRALIB
$ LINK  SPHERE,DIGS__LIBRARY:GRALIB/LIBRARY
_$!    Specify the output graphics file, and run SPHERE
$ DEFINE/USER  DIGF  SPHERE.DGF
$ RUN  SPHERE
_$!    See that the digf has been created
$ DIRECTORY/SIZE SPHERE.DGF

Directory USR$ROOT4:[BURCH.DIGS]

SPHERE.DGF;1           63

Total of 1 file, 63 blocks.
_$!    Fine, now run the post processor to rasterize and
_$!      output the picture
$ DEFINE/USER  DIGF  SPHERE.DGF
$ PRINTPP
PRINTPP - PRINTRONIX POST PROCESSOR FOR DIGS
COMMAND
PLOT
FILE HEADER  VERSION  1
BURCH     BURCH 2-FEB-84  10:04:47

COMMAND
QUIT
  Job 379 entered on queue TTC6
FORTRAN STOP
_$!   GREAT!, now go to the printronix and pick it up...
$ LOGOUT
.f