; AMAZE.ASM
;
; A maze generation/solution program.
;
; This program generates an 80x25 maze and directly draws the maze on the
; video display. It demonstrates the use of coroutines within a program.
.xlist
include stdlib.a
includelib stdlib.lib
.list
byp textequ <byte ptr>
dseg segment para public 'data'
; Constants:
;
; Define the "ToScreen" symbol (to any value) if the maze is 80x25 and you
; want to display it on the video screen.
ToScreen equ 0
; Maximum X and Y coordinates for the maze (matching the display).
MaxXCoord equ 80
MaxYCoord equ 25
; Useful X,Y constants:
WordsPerRow = MaxXCoord+2
BytesPerRow = WordsPerRow*2
StartX equ 1 ;Starting X coordinate for maze
StartY equ 3 ;Starting Y coordinate for maze
EndX equ MaxXCoord ;Ending X coordinate for maze
EndY equ MaxYCoord-1 ;Ending Y coordinate for maze
EndLoc = ( (EndY-1)*MaxXCoord + EndX-1)*2
StartLoc = ( (StartY-1)*MaxXCoord + StartX-1)*2
; Special 16-bit PC character codes for the screen for symbols drawn during
; maze generation. See the chapter on the video display for details.
ifdef mono ;Mono display adapter.
WallChar equ 7dbh ;Solid block character
NoWallChar equ 720h ;space
VisitChar equ 72eh ;Period
PathChar equ 72ah ;Asterisk
else ;Color display adapter.
WallChar equ 1dbh ;Solid block character
NoWallChar equ 0edbh ;space
VisitChar equ 0bdbh ;Period
PathChar equ 4e2ah ;Asterisk
endif
; The following are the constants that may appear in the Maze array:
Wall = 0
NoWall = 1
Visited = 2
; The following are the directions the demons can go in the maze
North = 0
South = 1
East = 2
West = 3
; Some important variables:
; The Maze array must contain an extra row and column around the
; outside edges for our algorithm to work properly.
Maze word (MaxYCoord+2) dup ((MaxXCoord+2) dup (Wall))
; The follow macro computes an index into the above array assuming
; a demon's X and Y coordinates are in the dl and dh registers, respectively.
; Returns index in the AX register
MazeAdrs macro
mov al, dh
mov ah, WordsPerRow ;Index into array is computed
mul ah ; by (Y*words/row + X)*2.
add al, dl
adc ah, 0
shl ax, 1 ;Convert to byte index
endm
; The following macro computes an index into the screen array, using the
; same assumptions as above. Note that the screen matrix is 80x25 whereas
; the maze matrix is 82x27; The X/Y coordinates in DL/DH are 1..80 and
; 1..25 rather than 0..79 and 0..24 (like we need). This macro adjusts
; for that.
ScrnAdrs macro
mov al, dh
dec al
mov ah, MaxXCoord
mul ah
add al, dl
adc ah, 0
dec ax
shl ax, 1
endm
; PCB for the main program. The last live demon will call this guy when
; it dies.
MainPCB pcb {}
; List of up to 32 demons.
MaxDemons = 32 ;Must be a power of two.
ModDemons = MaxDemons-1 ;Mask for MOD computation.
DemonList pcb MaxDemons dup ({})
DemonIndex byte 0 ;Index into demon list.
DemonCnt byte 0 ;Number of demons in list.
; Random number generator seed (we'll use our random number generator
; rather than the standard library's because we want to be able to specify
; an initial seed value).
Seed word 0
dseg ends
; The following is the segment address of the video display, change this
; from 0B800h to 0B000h if you have a monochrome display rather than a
; color display.
ScreenSeg segment at 0b800h
Screen equ this word ;Don't generate in date here!
ScreenSeg ends
cseg segment para public 'code'
assume cs:cseg, ds:dseg
; Totally bogus random number generator, but we don't need a really
; great one for this program. This code uses its own random number
; generator rather than the one in the Standard Library so we can
; allow the user to use a fixed seed to produce the same maze (with
; the same seed) or different mazes (by choosing different seeds).
RandNum proc near
push cx
mov cl, byte ptr Seed
and cl, 7
add cl, 4
mov ax, Seed
xor ax, 55aah
rol ax, cl
xor ax, Seed
inc ax
mov Seed, ax
pop cx
ret
RandNum endp
; Init- Handles all the initialization chores for the main program.
; In particular, it initializes the coroutine package, gets a
; random number seed from the user, and initializes the video display.
Init proc near
print
byte "Enter a small integer for a random number seed:",0
getsm
atoi
free
mov Seed, ax
; Fill the interior of the maze with wall characters, fill the outside
; two rows and columns with nowall values. This will prevent the demons
; from wandering outside the maze.
; Fill the first row with Visited values.
cld
mov cx, WordsPerRow
lesi Maze
mov ax, Visited
rep stosw
; Fill the last row with NoWall values.
mov cx, WordsPerRow
lea di, Maze+(MaxYCoord+1)*BytesPerRow
rep stosw
; Write a NoWall value to the starting position:
mov Maze+(StartY*WordsPerRow+StartX)*2, NoWall
; Write NoWall values along the two vertical edges of the maze.
lesi Maze
mov cx, MaxYCoord+1
EdgesLoop: mov es:[di], ax ;Plug the left edge.
mov es:[di+BytesPerRow-2], ax ;Plug the right edge.
add di, BytesPerRow
loop EdgesLoop
ifdef ToScreen
; Okay, fill the screen with WallChar values:
lesi Screen
mov ax, WallChar
mov cx, 2000
rep stosw
; Write appropriate characters to the starting and ending locations:
mov word ptr es:Screen+EndLoc, PathChar
mov word ptr es:Screen+StartLoc, NoWallChar
endif ;ToScreen
; Zero out the DemonList:
mov cx, (size pcb)*MaxDemons
lea di, DemonList
mov ax, dseg
mov es, ax
xor ax, ax
rep stosb
ret
Init endp
; CanStart- This function checks around the current position
; to see if the maze generator can start digging a new tunnel
; in a direction perpendicular to the current tunnel. You can
; only start a new tunnel if there are wall characters for at
; least two positions in the desired direction:
;
; ##
; *##
; ##
;
; If "*" is current position and "#" represent wall characters
; and the current direction is north or south, then it is okay
; for the maze generator to start a new path in the east dir-
; ection. Assuming "." represents a tunnel, you cannot start
; a new tunnel in the east direction if any of the following
; patterns occur:
;
; .# #. ## ## ## ##
; *## *## *.# *#. *## *##
; ## ## ## ## .# #.
;
; CanStart returns true (carry set) if we can start a new tunnel off the
; path being dug by the current demon.
;
; On entry, dl is demon's X-Coordinate
; dh is demon's Y-Coordinate
; cl is demon's direction
CanStart proc near
push ax
push bx
MazeAdrs ;Compute index to demon(x,y) in maze.
mov bx, ax
; CL contains the current direction, 0=north, 1=south, 2=east, 3=west.
; Note that we can test bit #1 for north/south (0) or east/west (1).
test cl, 10b ;See if north/south or east/west
jz NorthSouth
; If the demon is going in an east or west direction, we can start a new
; tunnel if there are six wall blocks just above or below the current demon.
; Note: We are checking if all values in these six blocks are Wall values.
; This code depends on the fact that Wall characters are zero and the sum
; of these six blocks will be zero if a move is possible.
mov al, byp Maze[bx+BytesPerRow*2] ;Maze[x, y+2]
add al, byp Maze[bx+BytesPerRow*2+2] ;Maze[x+1,y+2]
add al, byp Maze[bx+BytesPerRow*2-2] ;Maze[x-1,y+2]
je ReturnTrue
mov al, byp Maze[bx-BytesPerRow*2] ;Maze[x, y-2]
add al, byp Maze[bx-BytesPerRow*2+2] ;Maze[x+1,y-2]
add al, byp Maze[bx-BytesPerRow*2-2] ;Maze[x-1,y-2]
je ReturnTrue
ReturnFalse: clc ;Clear carry = false.
pop bx
pop ax
ret
; If the demon is going in a north or south direction, we can start a
; new tunnel if there are six wall blocks just to the left or right
; of the current demon.
NorthSouth: mov al, byp Maze[bx+4] ;Maze[x+2,y]
add al, byp Maze[bx+BytesPerRow+4] ;Maze[x+2,y+1]
add al, byp Maze[bx-BytesPerRow+4] ;Maze[x+2,y-1]
je ReturnTrue
mov al, byp Maze[bx-4] ;Maze[x-2,y]
add al, byp Maze[bx+BytesPerRow-4] ;Maze[x-2,y+1]
add al, byp Maze[bx-BytesPerRow-4] ;Maze[x-2,y-1]
jne ReturnFalse
ReturnTrue: stc ;Set carry = true.
pop bx
pop ax
ret
CanStart endp
; CanMove- Tests to see if the current demon (dir=cl, x=dl, y=dh) can
; move in the specified direction. Movement is possible if
; the demon will not come within one square of another tunnel.
; This function returns true (carry set) if a move is possible.
; On entry, CH contains the direction this code should test.
CanMove proc
push ax
push bx
MazeAdrs ;Put @Maze[x,y] into ax.
mov bx, ax
cmp ch, South
jb IsNorth
je IsSouth
cmp ch, East
je IsEast
; If the demon is moving west, check the blocks in the rectangle formed
; by Maze[x-2,y-1] to Maze[x-1,y+1] to make sure they are all wall values.
mov al, byp Maze[bx-BytesPerRow-4] ;Maze[x-2, y-1]
add al, byp Maze[bx-BytesPerRow-2] ;Maze[x-1, y-1]
add al, byp Maze[bx-4] ;Maze[x-2, y]
add al, byp Maze[bx-2] ;Maze[x-1, y]
add al, byp Maze[bx+BytesPerRow-4] ;Maze[x-2, y+1]
add al, byp Maze[bx+BytesPerRow-2] ;Maze[x-1, y+1]
je ReturnTrue
ReturnFalse: clc
pop bx
pop ax
ret
; If the demon is going east, check the blocks in the rectangle formed
; by Maze[x+1,y-1] to Maze[x+2,y+1] to make sure they are all wall values.
IsEast: mov al, byp Maze[bx-BytesPerRow+4] ;Maze[x+2, y-1]
add al, byp Maze[bx-BytesPerRow+2] ;Maze[x+1, y-1]
add al, byp Maze[bx+4] ;Maze[x+2, y]
add al, byp Maze[bx+2] ;Maze[x+1, y]
add al, byp Maze[bx+BytesPerRow+4] ;Maze[x+2, y+1]
add al, byp Maze[bx+BytesPerRow+2] ;Maze[x+1, y+1]
jne ReturnFalse
ReturnTrue: stc
pop bx
pop ax
ret
; If the demon is going north, check the blocks in the rectangle formed
; by Maze[x-1,y-2] to Maze[x+1,y-1] to make sure they are all wall values.
IsNorth: mov al, byp Maze[bx-BytesPerRow-2] ;Maze[x-1, y-1]
add al, byp Maze[bx-BytesPerRow*2-2];Maze[x-1, y-2]
add al, byp Maze[bx-BytesPerRow] ;Maze[x, y-1]
add al, byp Maze[bx-BytesPerRow*2] ;Maze[x, y-2]
add al, byp Maze[bx-BytesPerRow+2] ;Maze[x+1, y-1]
add al, byp Maze[bx-BytesPerRow*2+2];Maze[x+1, y-2]
jne ReturnFalse
stc
pop bx
pop ax
ret
; If the demon is going south, check the blocks in the rectangle formed
; by Maze[x-1,y+2] to Maze[x+1,y+1] to make sure they are all wall values.
IsSouth: mov al, byp Maze[bx+BytesPerRow-2] ;Maze[x-1, y+1]
add al, byp Maze[bx+BytesPerRow*2-2];Maze[x-1, y+2]
add al, byp Maze[bx+BytesPerRow] ;Maze[x, y+1]
add al, byp Maze[bx+BytesPerRow*2] ;Maze[x, y+2]
add al, byp Maze[bx+BytesPerRow+2] ;Maze[x+1, y+1]
add al, byp Maze[bx+BytesPerRow*2+2];Maze[x+1, y+2]
jne ReturnFalse
stc
pop bx
pop ax
ret
CanMove endp
; SetDir- Changes the current direction. The maze digging algorithm has
; decided to change the direction of the tunnel begin dug by one
; of the demons. This code checks to see if we CAN change the direction,
; and picks a new direction if possible.
;
; If the demon is going north or south, a direction change causes the demon
; to go east or west. Likewise, if the demon is going east or west, a
; direction change forces it to go north or south. If the demon cannot
; change directions (because it cannot move in the new direction for one
; reason or another), SetDir returns without doing anything. If a direction
; change is possible, then SetDir selects a new direction. If there is only
; one possible new direction, the demon is sent off in that direction.
; If the demon could move off in one of two different directions, SetDir
; "flips a coin" to choose one of the two new directions.
;
; This function returns the new direction in al.
SetDir proc near
test cl, 10b ;See if north/south
je IsNS ; or east/west direction.
; We're going east or west. If we can move EITHER north or south from
; this point, randomly choose one of the directions. If we can only
; move one way or the other, choose that direction. If we can't go either
; way, return without changing the direction.
mov ch, North ;See if we can move north
call CanMove
jnc NotNorth
mov ch, South ;See if we can move south
call CanMove
jnc DoNorth
call RandNum ;Get a random direction
and ax, 1 ;Make it north or south.
ret
DoNorth: mov ax, North
ret
NotNorth: mov ch, South
call CanMove
jnc TryReverse
DoSouth: mov ax, South
ret
; If the demon is moving north or south, choose a new direction of east
; or west, if possible.
IsNS: mov ch, East ;See if we can move East
call CanMove
jnc NotEast
mov ch, West ;See if we can move West
call CanMove
jnc DoEast
call RandNum ;Get a random direction
and ax, 1b ;Make it East or West
or al, 10b
ret
DoEast: mov ax, East
ret
DoWest: mov ax, West
ret
NotEast: mov ch, West
call CanMove
jc DoWest
; Gee, we can't switch to a perpendicular direction, see if we can
; turn around.
TryReverse: mov ch, cl
xor ch, 1
call CanMove
jc ReverseDir
; If we can't turn around (likely), then keep going in the same direction.
mov ah, 0
mov al, cl ;Stay in same direction.
ret
; Otherwise reverse direction down here.
ReverseDir: mov ah, 0
mov al, cl
xor al, 1
ret
SetDir endp
; Stuck- This function checks to see if a demon is stuck and cannot
; move in any direction. It returns true if the demon is
; stuck and needs to be killed.
Stuck proc near
mov ch, North
call CanMove
jc NotStuck
mov ch, South
call CanMove
jc NotStuck
mov ch, East
call CanMove
jc NotStuck
mov ch, West
call CanMove
NotStuck: ret
Stuck endp
; NextDemon- Searches through the demon list to find the next available
; active demon. Return a pointer to this guy in es:di.
NextDemon proc near
push ax
NDLoop: inc DemonIndex ;Move on to next demon,
and DemonIndex, ModDemons ; MOD MaxDemons.
mov al, size pcb ;Compute index into
mul DemonIndex ; DemonList.
mov di, ax ;See if the demon at this
add di, offset DemonList ; offset is active.
cmp byp [di].pcb.NextProc, 0
je NDLoop
mov ax, ds
mov es, ax
pop ax
ret
NextDemon endp
; Dig- This is the demon process.
; It moves the demon one position (if possible) in its current
; direction. After moving one position forward, there is
; a 25% chance that this guy will change its direction; there
; is a 25% chance this demon will spawn a child process to
; dig off in a perpendicular direction.
Dig proc near
; See if the current demon is stuck. If the demon is stuck, then we've
; go to remove it from the demon list. If it is not stuck, then have it
; continue digging. If it is stuck and this is the last active demon,
; then return control to the main program.
call Stuck
jc NotStuck
; Okay, kill the current demon.
; Note: this will never kill the last demon because we have the timer
; process running. The timer process is the one that always stops
; the program.
dec DemonCnt
; Since the count is not zero, there must be more demons in the demon
; list. Free the stack space associated with the current demon and
; then search out the next active demon and have at it.
MoreDemons: mov al, size pcb
mul DemonIndex
mov bx, ax
; Free the stack space associated with this process. Note this code is
; naughty. It assumes the stack is allocated with the Standard Library
; malloc routine that always produces a base address of 8.
mov es, DemonList[bx].regss
mov di, 8 ;Cheating!
free
; Mark the demon entry for this guy as unused.
mov byp DemonList[bx].NextProc, 0 ;Mark as unused.
; Okay, locate the next active demon in the list.
FndNxtDmn: call NextDemon
cocall ;Never returns
; If the demon is not stuck, then continue digging away.
NotStuck: mov ch, cl
call CanMove
jnc DontMove
; If we can move, then adjust the demon's coordinates appropriately:
cmp cl, South
jb MoveNorth
je MoveSouth
cmp cl, East
jne MoveWest
; Moving East:
inc dl
jmp MoveDone
MoveWest: dec dl
jmp MoveDone
MoveNorth: dec dh
jmp MoveDone
MoveSouth: inc dh
; Okay, store a NoWall value at this entry in the maze and output a NoWall
; character to the screen (if writing data to the screen).
MoveDone: MazeAdrs
mov bx, ax
mov Maze[bx], NoWall
ifdef ToScreen
ScrnAdrs
mov bx, ax
push es
mov ax, ScreenSeg
mov es, ax
mov word ptr es:[bx], NoWallChar
pop es
endif
; Before leaving, see if this demon shouldn't change direction.
DontMove: call RandNum
and al, 11b ;25% chance result is zero.
jne NoChangeDir
call SetDir
mov cl, al
NoChangeDir:
; Also, see if this demon should spawn a child process
call RandNum
and al, 11b ;Give it a 25% chance.
jne NoSpawn
; Okay, see if it's possible to spawn a new process at this point:
call CanStart
jnc NoSpawn
; See if we've already got MaxDemons active:
cmp DemonCnt, MaxDemons
jae NoSpawn
inc DemonCnt ;Add another demon.
; Okay, create a new demon and add him to the list.
push dx ;Save cur demon info.
push cx
; Locate a free slot for this demon
lea si, DemonList- size pcb
FindSlot: add si, size pcb
cmp byp [si].pcb.NextProc, 0
jne FindSlot
; Allocate some stack space for the new demon.
mov cx, 256 ;256 byte stack.
malloc
; Set up the stack pointer for this guy:
add di, 248 ;Point stack at end.
mov [si].pcb.regss, es
mov [si].pcb.regsp, di
; Set up the execution address for this guy:
mov [si].pcb.regcs, cs
mov [si].pcb.regip, offset Dig
; Initial coordinates and direction for this guy:
mov [si].pcb.regdx, dx
; Select a direction for this guy.
pop cx ;Retrieve direction.
push cx
call SetDir
mov ah, 0
mov [si].pcb.regcx, ax
; Set up other misc junk:
mov [si].pcb.regds, seg dseg
sti
pushf
pop [si].pcb.regflags
mov byp [si].pcb.NextProc, 1 ;Mark active.
; Restore current process' parameters
pop cx ;Restore current demon.
pop dx
NoSpawn:
; Okay, with all of the above done, it's time to pass control on to a new
; digger. The following cocall passes control to the next digger in the
; DemonList.
GetNextDmn: call NextDemon
; Okay, we've got a pointer to the next demon in the list (might be the
; same demon if there's only one), pass control to that demon.
cocall
jmp Dig
Dig endp
; TimerDemon- This demon introduces a 1/18th second delay between
; each cycle in the demon list. This slows down the
; maze generation so you can see the maze being built
; (which makes the program more interesting to watch).
TimerDemon proc near
push es
push ax
mov ax, 40h ;BIOS variable area
mov es, ax
mov ax, es:[6Ch] ;BIOS timer location
Wait4Change: cmp ax, es:[6Ch] ;BIOS changes this every
je Wait4Change ; 1/18th second.
cmp DemonCnt, 1
je QuitProgram
pop es
pop ax
call NextDemon
cocall
jmp TimerDemon
QuitProgram: cocall MainPCB ;Quit the program
TimerDemon endp
; What good is a maze generator program if it cannot solve the mazes it
; creates? SolveMaze finds the solution (if any) for this maze. It marks
; the solution path and the paths it tried, but failed on.
;
; function solvemaze(x,y:integer):boolean
sm_X textequ <[bp+6]>
sm_Y textequ <[bp+4]>
SolveMaze proc near
push bp
mov bp, sp
; See if we've just solved the maze:
cmp byte ptr sm_X, EndX
jne NotSolved
cmp byte ptr sm_Y, EndY
jne NotSolved
mov ax, 1 ;Return true.
pop bp
ret 4
; See if moving to this spot was an illegal move. There will be
; a NoWall value at this cell in the maze if the move is legal.
NotSolved: mov dl, sm_X
mov dh, sm_Y
MazeAdrs
mov bx, ax
cmp Maze[bx], NoWall
je MoveOK
mov ax, 0 ;Return failure
pop bp
ret 4
; Well, it is possible to move to this point, so place an appropriate
; value on the screen and keep searching for the solution.
MoveOK: mov Maze[bx], Visited
ifdef ToScreen
push es ;Write a "VisitChar"
ScrnAdrs ; character to the
mov bx, ax ; screen at this X,Y
mov ax, ScreenSeg ; position.
mov es, ax
mov word ptr es:[bx], VisitChar
pop es
endif
; Recusively call SolveMaze until we get a solution. Just call SolveMaze
; for the four possible directions (up, down, left, right) we could go.
; Since we've left "Visited" values in the Maze, we will not accidentally
; search back through the path we've already travelled. Furthermore, if
; we cannot go in one of the four directions, SolveMaze will catch this
; immediately upon entry (see the code at the start of this routine).
mov ax, sm_X ;Try the path at location
dec ax ; (X-1, Y)
push ax
push sm_Y
call SolveMaze
test ax, ax ;Solution?
jne Solved
push sm_X ;Try the path at location
mov ax, sm_Y ; (X, Y-1)
dec ax
push ax
call SolveMaze
test ax, ax ;Solution?
jne Solved
mov ax, sm_X ;Try the path at location
inc ax ; (X+1, Y)
push ax
push sm_Y
call SolveMaze
test ax, ax ;Solution?
jne Solved
push sm_X ;Try the path at location
mov ax, sm_Y ; (X, Y+1)
inc ax
push ax
call SolveMaze
test ax, ax ;Solution?
jne Solved
pop bp
ret 4
Solved:
ifdef ToScreen ;Draw return path.
push es
mov dl, sm_X
mov dh, sm_Y
ScrnAdrs
mov bx, ax
mov ax, ScreenSeg
mov es, ax
mov word ptr es:[bx], PathChar
pop es
mov ax, 1 ;Return true
endif
pop bp
ret 4
SolveMaze endp
; Here's the main program that drives the whole thing:
Main proc
mov ax, dseg
mov ds, ax
mov es, ax
meminit
call Init ;Initialize maze stuff.
lesi MainPCB ;Initialize coroutine
coinit ; package.
; Create the first demon.
; Set up the stack pointer for this guy:
mov cx, 256
malloc
add di, 248
mov DemonList.regsp, di
mov DemonList.regss, es
; Set up the execution address for this guy:
mov DemonList.regcs, cs
mov DemonList.regip, offset Dig
; Initial coordinates and direction for this guy:
mov cx, East ;Start off going east.
mov dh, StartY
mov dl, StartX
mov DemonList.regcx, cx
mov DemonList.regdx, dx
; Set up other misc junk:
mov DemonList.regds, seg dseg
sti
pushf
pop DemonList.regflags
mov byp DemonList.NextProc, 1 ;Demon is "active".
inc DemonCnt
mov DemonIndex, 0
; Set up the Timer demon:
mov DemonList.regsp+(size pcb), offset EndTimerStk
mov DemonList.regss+(size pcb), ss
; Set up the execution address for this guy:
mov DemonList.regcs+(size pcb), cs
mov DemonList.regip+(size pcb), offset TimerDemon
; Set up other misc junk:
mov DemonList.regds+(size pcb), seg dseg
sti
pushf
pop DemonList.regflags+(size pcb)
mov byp DemonList.NextProc+(size pcb), 1
inc DemonCnt
; Start the ball rolling.
mov ax, ds
mov es, ax
lea di, DemonList
cocall
; Wait for the user to press a key before solving the maze:
getc
mov ax, StartX
push ax
mov ax, StartY
push ax
call SolveMaze
; Wait for another keystroke before quitting:
getc
mov ax, 3 ;Clear screen and reset video mode.
int 10h
Quit: ExitPgm ;DOS macro to quit program.
Main endp
cseg ends
sseg segment para stack 'stack'
; Stack for the timer demon we create (we'll allocate the other
; stacks dynamically).
TimerStk byte 256 dup (?)
EndTimerStk word ?
; Main program's stack:
stk byte 512 dup (?)
sseg ends
zzzzzzseg segment para public 'zzzzzz'
LastBytes db 16 dup (?)
zzzzzzseg ends
end Main