高手看一下一个程序
DATA SEGMENT
DATA1 DB '?','24','$'
DATA2 DB '33','$'

STRING DB 's is : $'

DATA ENDS

PUBLIC JISUAN

CODE SEGMENT



JISUAN PROC FAR

ASSUME CS:CODE,DS:DATA
START: MOV AX,DATA
MOV DS,AX



MOV AL,DATA1
AND AL,DATA2
MOV DATA1,AL

; MUL CL


;MOV S, DX
;ADD S,30H

MOV AH,09H
MOV DX,OFFSET STRING
INT 21H

MOV AH,02H
MOV DL,BYTE PTR S
INT 21H

RET

JISUAN ENDP

CODE ENDS
END START




报错Microsoft (R) Macro Assembler Version 5.00
Copyright (C) Microsoft Corp 1981-1985, 1987. All rights reserved.

Object filename [add1.OBJ]:
Source listing [NUL.LST]:
Cross-reference [NUL.CRF]:
add1.asm(38): error A2009: Symbol not defined: S

50160 + 414960 Bytes symbol space free

0 Warning Errors
1 Severe Errors

G:\xpdos>

[解决办法]
问题出现在这两句上：
;MOV S, DX
;ADD S,30H

S在哪里做的定义？它又不是寄存器变量。
[解决办法]
汇编怎么到这里来了