PC/370 Maze Simulation

I've been busy with a lot of different things but I always manage to find time to amuse myself. The other day a thought popped in my head - somewhat randomly while I was outside cutting vines & branches, removing stumps & raking. I have 1.5 wooded acres & it was starting to look like a set from "Indiana Jones". Virginia creeper & some of the other types of ivy can be a menace - reaching high up into the tree tops & covering everything in sight. Yard work can be difficult but it's also relaxing & gives you time to think. So I thought of creating a simple maze in PC/370 using text characters in an input file. The screen is 24x80 and strings of X's would suffice for the walls. An asterisk (*) would mark the starting point and represent a little "maze runner" and an "at sign" (@) would mark the finishing spot. The only keys required would be Escape <ESC> to exit and the directional arrow keys (left, right, up & down). Sometimes when a thought crosses my mind it just has to run it's course... just like the little maze runner will run this course.


MAZE Template:

First thing I had to do... create an input template for the Maze. I decided to limit the maze area to the first 22 lines & keep the last two for key instructions (<ESC>=Exit) & basic messages. The program will work on any maze in this format. The assumption is that the maze area is within the proper 24x80 limitations & constrained by walls of X's - there is NO validation of the maze template. This is strictly an exercise of navigating through the maze. The starting point is designated in the template by an * and the end point is the @ symbol. Reaching the end simply produces the message "***WINNER***" without any other action. The little maze runner can continue happily if he likes until the <ESC> key is pressed.

Above: The MAZE template created in Notepad. START circled in YELLOW & the END in RED.

Note - Every line in the MAZE template ends with a $. This standard eliminates the need for a hard-coded $ within the program that is required for the WTO Supervisor Call (SCREEN Routine).

Creating/Running the MAZE Program:

On Friday evening (last night) my wife had to run to an appointment after dinner so, alone for a couple hours, I pulled out my laptop & cranked through some code. It was much easier than I envisioned. The maze runner either moves left or right +/- 1 position - or up & down +/- 80 positions (to account for an entire row). If that resulting spot has an 'X' the move is ignored. If the spot is the address of the @ sign the "Winner" message is displayed. I also drop a breadcrumb (.) at each spot the maze runner guy moves from as well as calculate the X/Y coordinates to display with each move.

Above: The program in action. Breadcrumbs create a trail. Current position circled in GREEN.

It was fun running the program & testing the capabilities. It was also gratifying reaching the end & watching the ***WINNER*** message appear.

Above: Sweet victory as the finish line is reached. *** WINNER ***

The little maze runner guy went down every corridor testing the strength of the walls. He couldn't bust through the walls but got a lot of exercise exploring the nooks & crannies...

Above: Every path & corridor has been traversed & marked with a breadcrumb.

Create ANY MAZE Template:

Multiple mazes can be created with the active one saved as TDMAZE.TXT (don't overlay without a backup after all that tedious work). Here's a minimal maze with the only constraints around the edges. The program works exactly the same. The positions of the start/end points are immaterial - in this example I flipped them starting in the bottom right & ending at the top left.

Above: Maze with Minimum Wall Constraints, Start (YELLOW) and End (RED) points.

A maze without internal walls looks more like a simplistic drawing application (due to the breadcrumb trail). I maneuvered the little maze runner guy to write my name - TONY.

Above: Writing my name within the free-form wall-less maze. Current position in GREEN.

TDMAZE.ALC - Main Processing Logic:

Logic is very simple. Read the text file & load each record into the array named MAZE. Record the occurrence of the start/end symbols (within the PARSE routine). Then move on to the Screen & Key handling. The SCREEN routine displays the 24x80 lines (via WTO SVC Calls) & reads the keystroke when pressed. All keys other than <ESC> & directional arrows are ignored. <ESC> exits the program. The arrows increment/decrement the current "little maze runner guy" position & tests if it's a wall (X). If not the maze runner moves along with his vacated position replaced with a breadcrumb (.).

***********************************************************************
*        MAINLINE PROCEDURE                                           *
***********************************************************************
         PRINT NOGEN
         SVC   @TRACE                        ISSUE SUPERVISOR CALL
         DC    CL4'IOF '                     KEYBOARD INTERRUPT OFF
*
         XFILI STDWKI                        OPEN INPUT  FILE
*
         LA    9,MAZE                        LOAD MAIN ADDRESS
GETI     EQU   *
         XREAD IREC,80                       READ INPUT RECORD
         BNZ   EOFI                          EOF - EXIT ROUTINE
*
         BAL   6,PARSE                       PARSE INPUT RECORD
*
         B     GETI                          READ NEXT RECORD
EOFI     EQU   *
         MVI   0(9),X'FF'                    MARK END OF TABLE
*
         MVC   MAZEMSG,MAZEMSG1              INIT MAZE MESSAGE
*
         MVI   VBITS,@BKWT                   SET BG(BLACK)/FG(WHITE)
         BAL   6,VRESET                      CHANGE SCREEN ATTRIBUTES
LOOP     EQU   *
         BAL   6,SCREEN                      BUILD SCREEN
*
         CLI   KEY,@K#ESC                    KEY = ESCAPE???
         BE    LOOPX                         YES - EXIT PLEASE
*
         L     3,MAZEPTR                     LOAD LAST CURSOR
*
         CLI   KEY,@K#ARWU                   KEY = ARROW UP???
         BE    LOOPZU                        YES - PROCESS KEY
         CLI   KEY,@K#ARWD                   KEY = ARROW DOWN???
         BE    LOOPZD                        YES - PROCESS KEY
         CLI   KEY,@K#ARWL                   KEY = ARROW LEFT???
         BE    LOOPZL                        YES - PROCESS KEY
         CLI   KEY,@K#ARWR                   KEY = ARROW RIGHT???
         BNE   LOOP                          NO  - DISPLAY SCREEN
*
*        ARROW KEYS
*
LOOPZR   EQU   *
         AH    3,=Y(1)                       Y INCREMENT POINTER
         MVC   MAZEKEY,=CL6'RIGHT'           TRACK KEY DIRECTION
         B     LOOPZ1                        TEST NEW POSITION
LOOPZL   EQU   *
         SH    3,=Y(1)                       Y DECREMENT POINTER
         MVC   MAZEKEY,=CL6'LEFT'            TRACK KEY DIRECTION
         B     LOOPZ1                        TEST NEW POSITION
LOOPZD   EQU   *
         AH    3,=Y(80)                      X INCREMENT POINTER
         MVC   MAZEKEY,=CL6'DOWN'            TRACK KEY DIRECTION
         B     LOOPZ1                        TEST NEW POSITION
LOOPZU   EQU   *
         SH    3,=Y(80)                      X DECREMENT POINTER
         MVC   MAZEKEY,=CL6'UP'              TRACK KEY DIRECTION
LOOPZ1   EQU   *
         CLI   0(3),C'X'                     HITTING A WALL???
         BE    LOOP                          YES - IGNORE MOVE
*
         L     4,MAZEPTR                     LOAD CURRENT CURSOR
         MVI   0(4),C'.'                     DROP BREADCRUMB
         C     3,MAZEEND                     MAZE END REACHED?
         BE    LOOPEND                       YES - VICTORY!!!
         ST    3,MAZEPTR                     RESET CURRENT CURSOR
         MVI   0(3),C'*'                     MOVE MAZE RUNNER
         BAL   6,POSCALC                     POSITION CALCULATOR
         B     LOOP                          DISPLAY SCREEN AGAIN
LOOPEND  EQU   *
         MVC   MAZEMSG,MAZEMSG3              WINNER MESSAGE!
         B     LOOP                          DISPLAY SCREEN AGAIN
LOOPX    EQU   *
         B     RETURN                        EXIT PROGRAM PLEASE
***********************************************************************

The Position Calculation serves no purpose other than to display the coordinates in a message. Just a nice aesthetic touch to the application... Because of the wall constraints the X/Y calculation is simple - no need to test for a remainder of zero when dividing by 80 - it will never be zero.

***********************************************************************
*        POSITION CALCULATION                                         *
***********************************************************************
         DC    F'0'                          RETURN ADDRESS SAVE AREA
POSCALC  EQU   *
         ST    6,*-4                         SAVE RETURN ADDRESS
*
         L     6,MAZEPTR                     LOAD CURSOR ADDRESS
         S     6,=A(MAZE)                    SUBSTRACT MAZE ADDRESS
         CVD   6,DUBB                        CONVERT TO DECIMAL
         DP    DUBB,=P'80'                   DIVIDE BY 80 COLUMNS
         ZAP   XX,DUBB+4(2)                  EXTRACT X-COORDINATE
         ZAP   YY,DUBB+6(2)                  EXTRACT Y-COORDINATE
*
         MVC   MAZEMSG,MAZEMSG2              MOVE MAZE MESSAGE 2
         UNPK  MAZEMSG+5(3),XX               UNPACK X-COORDINATE
         UNPK  MAZEMSG+9(3),YY               UNPACK Y-COORDINATE
         OI    MAZEMSG+7,X'F0'               TURN ON ZONE BITS
         OI    MAZEMSG+11,X'F0'              TURN ON ZONE BITS
         MVC   MAZEMSG+14(6),MAZEKEY         MOVE MAZE KEY
POSCALCX EQU   *
         L     6,POSCALC-4                   RESTORE LINK REGISTER
         BR    6                             BRANCH ON LINK REGISTER
***********************************************************************
This was not an elaborate exercise. Tracking the "little maze runner" & the walls was pretty easy. After the Assembly/Link it worked perfectly on the very first test - the maze guy was flying off the walls! Although, I was very diligent with my proofreading.

TDMAZE.ALC - Full Source Code:

Full source code minus the Copybooks for Screen, Video & Key handling. Also, some commonly used variables & copybooks may appear although they aren't utilized - this makes cloning for other exercises quicker.

         TITLE 'TDMAZE   - PC/370 4.2 // DELIA'
***********************************************************************
*                                                                     *
*        MODULE:  TDMAZE.                                             *
*        AUTHOR:  TONY DELIA.                                         *
*          DATE:  03/06/2020.                                         *
*          DESC:  PC/370 SIMPLE MAZE ALGORITHM.                       *
*          NOTE:  PC/370 RELEASE 4.2                                  *
*                                                                     *
***********************************************************************
         EJECT
***********************************************************************
*        T  D  M  A  Z  E           P  R  O  G  R  A  M               *
***********************************************************************
TDMAZE   START 0                             START PROGRAM
         STM   14,12,12(13)                  SAVE REGISTERS
         LR    12,15                         LOAD PROGRAM ENTRY POINT
         USING TDMAZE+0*4096,12              BASE REGISTER 1
         L     11,BASE2                      LOAD BASE REGISTER 2
         USING TDMAZE+1*4096,11              TELL ASSEMBLER ABOUT BASE2
         L     10,BASE3                      LOAD BASE REGISTER 3
         USING TDMAZE+2*4096,10              TELL ASSEMBLER ABOUT BASE3
         ST    13,SAVE+4                     SAVE EXTERNAL SAVE ADDRESS
         LR    14,13                         XFER ADDRESS TO TEMP R14
         LA    13,SAVE                       LOAD INTERNAL SAVE ADDRESS
         ST    13,8(14)                      SAVE IN EXTERNAL SAVE AREA
         B     GO                            BRANCH TO PROCESSING RTN
***********************************************************************
RETURN   EQU   *                             TIME TO RETURN
         L     13,SAVE+4                     RESTORE REGISTER 13
         LM    14,12,12(13)                  RESTORE REMAINING REGS
         SR    15,15                         CLEAR RETURN CODE
         BR    14                            BRANCH TO CALLING PROGRAM
***********************************************************************
SAVE     DC    18F'0'                        S A V E   A R E A
***********************************************************************
BASE2    DC    A(TDMAZE+1*4096)              BASE2 DISPLACEMENT
BASE3    DC    A(TDMAZE+2*4096)              BASE3 DISPLACEMENT
***********************************************************************
GO       EQU   *                             BEGIN PROCESSING ...
***********************************************************************
         EJECT
***********************************************************************
*        MAINLINE PROCEDURE                                           *
***********************************************************************
         PRINT NOGEN
         SVC   @TRACE                        ISSUE SUPERVISOR CALL
         DC    CL4'IOF '                     KEYBOARD INTERRUPT OFF
*
         XFILI STDWKI                        OPEN INPUT  FILE
*
         LA    9,MAZE                        LOAD MAIN ADDRESS
GETI     EQU   *
         XREAD IREC,80                       READ INPUT RECORD
         BNZ   EOFI                          EOF - EXIT ROUTINE
*
         BAL   6,PARSE                       PARSE INPUT RECORD
*
         B     GETI                          READ NEXT RECORD
EOFI     EQU   *
         MVI   0(9),X'FF'                    MARK END OF TABLE
*
         MVC   MAZEMSG,MAZEMSG1              INIT MAZE MESSAGE
*
         MVI   VBITS,@BKWT                   SET BG(BLACK)/FG(WHITE)
         BAL   6,VRESET                      CHANGE SCREEN ATTRIBUTES
LOOP     EQU   *
         BAL   6,SCREEN                      BUILD SCREEN
*
         CLI   KEY,@K#ESC                    KEY = ESCAPE???
         BE    LOOPX                         YES - EXIT PLEASE
*
         L     3,MAZEPTR                     LOAD LAST CURSOR
*
         CLI   KEY,@K#ARWU                   KEY = ARROW UP???
         BE    LOOPZU                        YES - PROCESS KEY
         CLI   KEY,@K#ARWD                   KEY = ARROW DOWN???
         BE    LOOPZD                        YES - PROCESS KEY
         CLI   KEY,@K#ARWL                   KEY = ARROW LEFT???
         BE    LOOPZL                        YES - PROCESS KEY
         CLI   KEY,@K#ARWR                   KEY = ARROW RIGHT???
         BNE   LOOP                          NO  - DISPLAY SCREEN
*
*        ARROW KEYS
*
LOOPZR   EQU   *
         AH    3,=Y(1)                       Y INCREMENT POINTER
         MVC   MAZEKEY,=CL6'RIGHT'           TRACK KEY DIRECTION
         B     LOOPZ1                        TEST NEW POSITION
LOOPZL   EQU   *
         SH    3,=Y(1)                       Y DECREMENT POINTER
         MVC   MAZEKEY,=CL6'LEFT'            TRACK KEY DIRECTION
         B     LOOPZ1                        TEST NEW POSITION
LOOPZD   EQU   *
         AH    3,=Y(80)                      X INCREMENT POINTER
         MVC   MAZEKEY,=CL6'DOWN'            TRACK KEY DIRECTION
         B     LOOPZ1                        TEST NEW POSITION
LOOPZU   EQU   *
         SH    3,=Y(80)                      X DECREMENT POINTER
         MVC   MAZEKEY,=CL6'UP'              TRACK KEY DIRECTION
LOOPZ1   EQU   *
         CLI   0(3),C'X'                     HITTING A WALL???
         BE    LOOP                          YES - IGNORE MOVE
*
         L     4,MAZEPTR                     LOAD CURRENT CURSOR
         MVI   0(4),C'.'                     DROP BREADCRUMB
         C     3,MAZEEND                     MAZE END REACHED?
         BE    LOOPEND                       YES - VICTORY!!!
         ST    3,MAZEPTR                     RESET CURRENT CURSOR
         MVI   0(3),C'*'                     MOVE MAZE RUNNER
         BAL   6,POSCALC                     POSITION CALCULATOR
         B     LOOP                          DISPLAY SCREEN AGAIN
LOOPEND  EQU   *
         MVC   MAZEMSG,MAZEMSG3              WINNER MESSAGE!
         B     LOOP                          DISPLAY SCREEN AGAIN
LOOPX    EQU   *
         B     RETURN                        EXIT PROGRAM PLEASE
***********************************************************************
         EJECT
***********************************************************************
*        PARSE RECORD                        R9=MAZE                  *
***********************************************************************
         DC    F'0'                          RETURN ADDRESS SAVE AREA
PARSE    EQU   *
         ST    6,*-4                         SAVE RETURN ADDRESS
*
         CLI   0(9),X'FF'                    MAZE TABLE FULL??
         BE    PARSEX                        YES - EXIT ROUTINE
*
         MVC   0(80,9),IREC                  STORE MAZE DATA
*
         LA    7,79                          LOAD MAZE COUNT
         LR    8,9                           LOAD MAZE ADDRESS
*
PARL1A   BC    0,PARL1B                      BYPASS WHEN FOUND
         CLI   0(8),C'*'                     STARTING TOKEN ???
         BNE   PARL1B                        NO  - CONTINUE PLEASE
         ST    8,MAZEBEG                     YES - STORE ADDRESS
         ST    8,MAZEPTR                     SET MAZE CURSOR
         OI    PARL1A+1,X'F0'                SET BYPASS SWITCH
*
PARL1B   BC    0,PARBUMP                     BYPASS WHEN FOUND
         CLI   0(8),C'@'                     FINISH TOKEN???
         BNE   PARBUMP                       NO  - CONTINUE PLEASE
         ST    8,MAZEEND                     YES - STORE ADDRESS
         OI    PARL1B+1,X'F0'                SET BYPASS SWITCH
PARBUMP  EQU   *
         LA    8,1(,8)                       BUMP TABLE POINTER
         BCT   7,PARL1A                      TEST NEXT POSITION
PARGO    EQU   *
         LA    9,80(,9)                      BUMP TABLE POINTER
PARSEX   EQU   *
         L     6,PARSE-4                     RESTORE LINK REGISTER
         BR    6                             BRANCH ON LINK REGISTER
***********************************************************************
         EJECT
***********************************************************************
*        POSITION CALCULATION                                         *
***********************************************************************
         DC    F'0'                          RETURN ADDRESS SAVE AREA
POSCALC  EQU   *
         ST    6,*-4                         SAVE RETURN ADDRESS
*
         L     6,MAZEPTR                     LOAD CURSOR ADDRESS
         S     6,=A(MAZE)                    SUBSTRACT MAZE ADDRESS
         CVD   6,DUBB                        CONVERT TO DECIMAL
         DP    DUBB,=P'80'                   DIVIDE BY 80 COLUMNS
         ZAP   XX,DUBB+4(2)                  EXTRACT X-COORDINATE
         ZAP   YY,DUBB+6(2)                  EXTRACT Y-COORDINATE
*
         MVC   MAZEMSG,MAZEMSG2              MOVE MAZE MESSAGE 2
         UNPK  MAZEMSG+5(3),XX               UNPACK X-COORDINATE
         UNPK  MAZEMSG+9(3),YY               UNPACK Y-COORDINATE
         OI    MAZEMSG+7,X'F0'               TURN ON ZONE BITS
         OI    MAZEMSG+11,X'F0'              TURN ON ZONE BITS
         MVC   MAZEMSG+14(6),MAZEKEY         MOVE MAZE KEY
POSCALCX EQU   *
         L     6,POSCALC-4                   RESTORE LINK REGISTER
         BR    6                             BRANCH ON LINK REGISTER
***********************************************************************
         EJECT
***********************************************************************
*        BUILD SCREEN                                                 *
***********************************************************************
         DC    F'0'                          RETURN ADDRESS SAVE AREA
SCREEN   EQU   *
         ST    6,*-4                         SAVE RETURN ADDRESS
*
         LA    5,SCTAB                       LOAD TABLE ADDRESS
SC1LP    EQU   *
         CLI   0(5),X'FF'                    END OF TABLE ???
         BE    SC2LP                         YES - EXIT LOOP PLEASE
*
         MVC   VXYS,0(5)                     MOVE CURSOR POSITION
         BAL   6,VXYSET                      SET CURSOR POSITION
         L     2,4(5)                        LOAD MESSAGE ADDRESS
         SVC   @WTO                          ISSUE SUPERVISOR CALL
*
         LA    5,8(,5)                       BUMP TABLE POINTER
         B     SC1LP                         TEST NEXT TABLE ENTRY
SC2LP    EQU   *
*
*        ACCEPT KEYSTROKE
*
         BAL   6,KBGET                       READ KEYBOARD INPUT
         MVC   KEY,KBCHR                     STORE KEYSTROKE
*
         CLI   KEY,@K#ESC                    KEY = ESCAPE ???
         BE    SCREENX                       YES - EXIT ROUTINE
*
         CLI   KEY,@K#ARWU                   KEY = ARROW UP???
         BE    SCREENX                       YES - EXIT ROUTINE
         CLI   KEY,@K#ARWD                   KEY = ARROW DOWN???
         BE    SCREENX                       YES - EXIT ROUTINE
         CLI   KEY,@K#ARWL                   KEY = ARROW LEFT???
         BE    SCREENX                       YES - EXIT ROUTINE
         CLI   KEY,@K#ARWR                   KEY = ARROW RIGHT???
         BNE   SC2LP                         NO  - ENTER NEW KEY
SCREENX  EQU   *
         L     6,SCREEN-4                    RESTORE LINK REGISTER
         BR    6                             BRANCH ON LINK REGISTER
***********************************************************************
         EJECT
***********************************************************************
*        WORKING STORAGE                                              *
***********************************************************************
DUBB     DC    D'0'                          DOUBLEWORD
FULL     DC    F'0'                          FULLWORD
HALF     DC    H'0'                          HALFWORD
XX       DC    PL2'0'                        X-POINTER
YY       DC    PL2'0'                        Y-POINTER
KEY      DC    CL1' '                        KEY STROKE (@RDKEY)
CHAR     DC    CL1' ',C'$'                   KEY CHARACTER
@YES     EQU   C'Y'                          YES
@NO      EQU   C'N'                          NO
@ESC     EQU   27                            ESCAPE KEY
@CR      EQU   13                            CARRIAGE RETURN
@LF      EQU   10                            LINE FEED
@KEYLO   EQU   32                            ASCII KEY - LO VALUE
@KEYHI   EQU   126                           ASCII KEY - HI VALUE
BLOCK    DC    AL1(219)                      BLOCK CHARACTER
***********************************************************************
*        DATA CONTROL BLOCK SET UP                                    *
***********************************************************************
STDWKI   DC    CL64'C:\PC370\TDMAZE.TXT'
***********************************************************************
*        INPUT RECORD AREA                                            *
***********************************************************************
IREC     DC    CL80' '                       INPUT RECORD
***********************************************************************
         LTORG                               LITERAL POOL
***********************************************************************
*        COPYBOOKS                                                    *
***********************************************************************
         COPY  CPY/TDBOX.CPY                 COPYBOOK - BOX DISPLAY
         COPY  CPY/TDVID.CPY                 COPYBOOK - VIDEO UTILITY
         COPY  CPY/TDKBD.CPY                 COPYBOOK - KEYBOARD INPUT
         COPY  CPY/TDKEY.CPY                 COPYBOOK - KEYSTROKES
         COPY  CPY/TDCLR.CPY                 COPYBOOK - COLORS
         COPY  CPY/TDSVC.CPY                 COPYBOOK - SUPERVISOR
***********************************************************************
*        BOX COMPONENTS (COORDINATES/FRAME)                           *
***********************************************************************
BXTAB    DS    0F
         DC    AL1(0,0,23,79)                BOX COORDINATES/FRAME
***********************************************************************
*        SCREEN DISPLAY COMPONENTS                                    *
***********************************************************************
SCTAB    DS    0F
         DC    AL1(0,0,0,0),A(MAZE+80*0)     SCREEN COORDINATES/MSG
         DC    AL1(0,0,1,0),A(MAZE+80*1)     SCREEN COORDINATES/MSG
         DC    AL1(0,0,2,0),A(MAZE+80*2)     SCREEN COORDINATES/MSG
         DC    AL1(0,0,3,0),A(MAZE+80*3)     SCREEN COORDINATES/MSG
         DC    AL1(0,0,4,0),A(MAZE+80*4)     SCREEN COORDINATES/MSG
         DC    AL1(0,0,5,0),A(MAZE+80*5)     SCREEN COORDINATES/MSG
         DC    AL1(0,0,6,0),A(MAZE+80*6)     SCREEN COORDINATES/MSG
         DC    AL1(0,0,7,0),A(MAZE+80*7)     SCREEN COORDINATES/MSG
         DC    AL1(0,0,8,0),A(MAZE+80*8)     SCREEN COORDINATES/MSG
         DC    AL1(0,0,9,0),A(MAZE+80*9)     SCREEN COORDINATES/MSG
         DC    AL1(0,0,10,0),A(MAZE+80*10)   SCREEN COORDINATES/MSG
         DC    AL1(0,0,11,0),A(MAZE+80*11)   SCREEN COORDINATES/MSG
         DC    AL1(0,0,12,0),A(MAZE+80*12)   SCREEN COORDINATES/MSG
         DC    AL1(0,0,13,0),A(MAZE+80*13)   SCREEN COORDINATES/MSG
         DC    AL1(0,0,14,0),A(MAZE+80*14)   SCREEN COORDINATES/MSG
         DC    AL1(0,0,15,0),A(MAZE+80*15)   SCREEN COORDINATES/MSG
         DC    AL1(0,0,16,0),A(MAZE+80*16)   SCREEN COORDINATES/MSG
         DC    AL1(0,0,17,0),A(MAZE+80*17)   SCREEN COORDINATES/MSG
         DC    AL1(0,0,18,0),A(MAZE+80*18)   SCREEN COORDINATES/MSG
         DC    AL1(0,0,19,0),A(MAZE+80*19)   SCREEN COORDINATES/MSG
         DC    AL1(0,0,20,0),A(MAZE+80*20)   SCREEN COORDINATES/MSG
         DC    AL1(0,0,21,0),A(MAZE+80*21)   SCREEN COORDINATES/MSG
         DC    AL1(0,0,22,0),A(MAZE+80*22)   SCREEN COORDINATES/MSG
         DC    AL1(0,0,23,0),A(MAZE+80*23)   SCREEN COORDINATES/MSG
         DC    AL1(0,0,22,36),A(MAZEMSG)     SCREEN COORDINATES/MSG
         DC    XL1'FF'                       END OF TABLE
***********************************************************************
*        MAZE                                                         *
***********************************************************************
MAZEKEY  DC    CL6' '                        MAZE MESSAGE KEY
MAZEMSG1 DC    CL40'USE ARROW KEYS'          MAZE MESSAGE 1
MAZEMSG2 DC    CL40'X,Y=(999,999) XXXXXX'    MAZE MESSAGE 2
MAZEMSG3 DC    CL40'*** WINNER ***'          MAZE MESSAGE 3
MAZEMSG  DC    CL40' ',C'$'                  MAZE MESSAGE TEXT AREA
MAZEPTR  DC    A(MAZE)                       MAZE POINTER - CURSOR
MAZEBEG  DC    A(MAZE)                       MAZE POINTER - BEGIN
MAZEEND  DC    A(MAZE)                       MAZE POINTER - END
MAZE     DC    24CL80' '                     24X80 MAZE TEMPLATE
         DC    XL1'FF'                       END OF MAZE TEMPLATE
***********************************************************************
         END   TDMAZE

Hope someone out there enjoys this fun exercise... now I can focus on yard work again.