TASM: Generating a simple calculator - arrays

Question

i am trying to make a simple calculator in TASM, its not done yet, i am trying to figure out addition part but i am stuck because of Operands type do not match, here is what i have;
;FILENAME: SimpleClc.asm
;FILE FORMAT: EXE
PAGE 55,132
.386
STACK_SEG SEGMENT STACK USE16
DB 100 DUP(?)
STACK_SEG ENDS
DATA_SEG SEGMENT 'DATA' USE16
ADDITION MACRO Result,Char1,Char2
MOV AX,Char1
CWD
ADD AX,Char2,
MOV Result,AX
ENDM
SUBTRACTION MACRO Char1, Char2
SUB Char1,Char2
ENDM
DIVISION MACRO Char1, Char2
DIV Char1,Char2
ENDM
MULTIPLICATION MACRO Char1, Char2
MUL Char1,Char2
ENDM
Mainmsg DB 'Please enter a algebraic command line: $'
ErMessage DB 'Error!!', 0DH, 0AH
DB 'INPUT FORMAT:Operand1 Operator Operand',0DH, 0AH
DB 'Operand: Decimal Numbers',0DH, 0AH
DB 'Operator: + -'
INCHAR DB 21
Res DB 10 dup('$')
INCDAT DB 21 dup('$')
VarX DB 10 dup('$')
VarY DB 10 dup('$')
DATA_SEG ENDS
CODE_SEG SEGMENT PARA 'CODE' PUBLIC USE16
ASSUME CS:CODE_SEG, DS:DATA_SEG, SS:STACK_SEG
MAIN PROC FAR
PUSH DS ;INITIATE THE PROGRAM
XOR AX,AX
PUSH AX
MOV AX,DATA_SEG
MOV DS,AX
AGAIN:
LEA DX,Mainmsg ;PRINT MESSAGE
MOV AH,9
INT 21H
MOV DX, OFFSET INCHAR
MOV AH,0AH
INT 21H
MOV DX, OFFSET INCHAR
MOV AH,0AH
INT 21H
LEA DX,INCDAT ;Writing the incoming input
MOV AH,9
INT 21H
MOV DI,OFFSET INCDAT
MOV AL, [DI]
CMP AL, 9
JLE OPERAND ; jump if less or equal
JG ERRORMESSAGE ; jump if not less or equal
INC DI
OPERAND:
MOV AL, [DI]
CMP AL, '+'
JE LASTOPERAND
CMP AL, '-'
JE LASTOPERAND
CMP AL, '*'
JE LASTOPERAND
CMP AL, '/'
JE LASTOPERAND
JMP ERRORMESSAGE
INC DI
LASTOPERAND:
MOV AL, [DI]
CMP AL, 9
JLE OPERATION ; jump if less or equal
JG ERRORMESSAGE ; jump if not less or equal
OPERATION:
CMP AL, '+'
JE ADDITION1
JMP AGAIN
ADDITION1:
MOV DI,OFFSET INCDAT
MOV AL,[DI]
MOV VarX,AL
MOV AL,[DI+2]
MOV VarY,AL
ADDITION Res,VarX,VarY
JMP AGAIN
CMP AL, '-'
JE SUBTRACTION1
JMP AGAIN
SUBTRACTION1:
CMP AL, '*'
JE MULTIPLICATION1
JMP AGAIN
MULTIPLICATION1:
JMP AGAIN
CMP AL, '/'
JE DIVISION1
JMP AGAIN
DIVISION1:
ERRORMESSAGE:
LEA DX,ErMessage ;PRINT MESSAGE
MOV AH,9
INT 21H
MAIN ENDP
CODE_SEG ENDS
END MAIN
I know it looks quite messy right now, it is just because i am trying bunch of things at the same time, btw my calculator will not calculate results that are greater than 10. Thanks for help.Any comment will be appreciated.

Answer 1

Ups, it is hard to digit all the linenumbers.
To place code inside the data segment is not the best idea.
For what this following instruction are good?:
PUSH DS ; pushing the old address of DS to the stack
XOR AX,AX
PUSH AX ; pushing a zero word to the stack
And at last how to terminate the programm?
I am not sure, but maybe the errors occur for using labelnames that starts similar like the names of assembler mnemonics.
And why using the input function one after another for to override the same buffer?
MOV DX, OFFSET INCHAR
MOV AH,0AH
INT 21H
MOV DX, OFFSET INCHAR
MOV AH,0AH
INT 21H