.MODEL SMALL
.DATA
GMSG DB ‘Computer TIC TAC TOE.’,0DH,0AH
DB ‘User is X, computer is O’,0DH,0AH,0DH,0AH,’$’
BOARD DB ‘123456789’
BTXT DB 0DH,0AH
DB ‘ | | ‘,0DH,0AH
DB ‘———‘,0DH,0AH
DB ‘ | | ‘,0DH,0AH
DB ‘———‘,0DH,0AH
DB ‘ | | ‘,0DH,0AH,0DH,0AH,’$’
BPOS DB 2,6,10,24,28,32,46,50,54
PMSG DB ‘Enter your move (0 to 9): $’
PIM1 DB 0DH,0AH,’That move does not make sense, try again.’,0DH,0AH,’$’
PIM2 DB 0DH,0AH,’That square is occupied, try again.’,0DH,0AH,’$’
CMSG DB ‘I choose square $’
CRLF DB 0DH,0AH,’$’
WINS DW 1,2,3, 4,5,6, 7,8,9
DW 1,4,7, 2,5,8, 3,6,9
DW 1,5,9, 3,5,7
XWIN DB ‘X wins the game!’,0DH,0AH,’$’
OWIN DB ‘O wins the game!’,0DH,0AH,’$’
MTIE DB ‘The game is a tie.’,0DH,0AH,’$’

.CODE
.STARTUP
LEA DX,GMSG
MOV AH,9
INT 21H
CALL SHOWBRD
NEXT: CALL PMOVE
CALL SHOWBRD
CALL CHECK
JZ EXIT
CALL CMOVE
CALL SHOWBRD
CALL CHECK
JZ EXIT
JMP NEXT
EXIT: .EXIT

SHOWBRD PROC NEAR
MOV CX,9
SUB SI,SI
LBC: MOV AL,BPOS[SI]
CBW
MOV DI,AX
MOV AL,BOARD[SI]
MOV BTXT[DI],AL
INC SI
LOOP LBC
LEA DX,BTXT
MOV AH,9
INT 21H
RET
SHOWBRD ENDP

PMOVE PROC NEAR
LEA DX,PMSG
MOV AH,9
INT 21H
MOV AH,1
INT 21H
CMP AL,’1′
JC BPM
CMP AL,’9’+1
JNC BPM
SUB AL,31H
CBW
MOV SI,AX
MOV AL,BOARD[SI]
CMP AL,’X’
JZ PSO
CMP AL,’O’
JZ PSO
MOV BOARD[SI],’X’
LEA DX,CRLF
MOV AH,9
INT 21H
RET
BPM: LEA DX,PIM1
STP: MOV AH,9
INT 21H
JMP PMOVE
PSO: LEA DX,PIM2
JMP STP
RET
PMOVE ENDP

CMOVE PROC NEAR
SUB SI,SI
NCM: MOV AL,BOARD[SI]
CMP AL,’X’
JZ STN
CMP AL,’O’
JZ STN
MOV BOARD[SI],’O’
MOV AX,SI
PUSH AX
LEA DX,CMSG
MOV AH,9
INT 21H
POP DX
ADD DL,31H
MOV AH,2
INT 21H
LEA DX,CRLF
MOV AH,9
INT 21H
RET
STN: INC SI
JMP NCM
CMOVE ENDP

CHECK PROC NEAR
SUB SI,SI
MOV CX,8
CAT: MOV DI,WINS[SI]
MOV AH,BOARD[DI-1]
MOV DI,WINS[SI+2]
MOV BL,BOARD[DI-1]
MOV DI,WINS[SI+4]
MOV BH,BOARD[DI-1]
ADD SI,6
CMP AH,BL
JNZ NMA
CMP AH,BH
JNZ NMA
CMP AH,’X’
JNZ WIO
LEA DX,XWIN
JMP EXC
WIO: LEA DX,OWIN
JMP EXC
NMA: LOOP CAT
SUB SI,SI
CFB: MOV AL,BOARD[SI]
CMP AL,’X’
JZ IAH
CMP AL,’O’
JZ IAH
RET
IAH: INC SI
LOOP CFB
LEA DX,MTIE