Question

I need help with this program. It is in Irvine MASM Assembly Language.

You are to write a program to compute the results of a postfix expression. The expression has the format operand operand operator   where the operator can be +, -, *. You must use a stack to evaluate the expressions. (The system Stack will not work.) Print out the input expression and the results of the evaluation. Read the data from a file and output to a file. Use functions/procedures. Turn in the assembly listing (.lst) and output files.

Input File:

5 9 +
82 41 -
3 10 4 - *
13 18 * 140 80 - +
1 2 3 4 5 6 7 + + + + + +
1998 900 - 98 -
4596 4300 96 + - 2 2 * *
88 45 + 22 9 * 16 7 93 - * + 55 - +
5 2 * 10 40 * + 5 20 * 70 50 - 20 30 40 + + - + 3 - +
55 66 + 17 3 + 20 10 + * +
5 2 * 10 40 * + 5 20 * 70 50 - 20 30 40 + + - + 3 - +
123456 654321 + 123456 654321 + -
99999 2000 *

Answer 1

.MODEL  SMALL
.DATA
        NL      DB      0DH,0AH,\'$\'
.CODE

MAIN    PROC
        MOV     AX,@DATA
        MOV     DS,AX
READ_CHAR:
        MOV     AH,01H
        INT     21H
        CMP     AL,0DH
        JE      END_OF_SCAN

        CMP     AL,2BH
        JE      EVAL_PLUS

        CMP     AL,2DH
        JE      EVAL_MINUS
CONV_ASCII:
        CMP     AL,39H
        JLE     CONVERT

        SUB     AL,37H
        JMP     TO_PUSH
CONVERT:
        SUB     AL,30H
TO_PUSH:
        MOV     AH,0
        PUSH    AX
        JMP     READ_CHAR
EVAL_PLUS:
        POP     AX
        POP     BX

        ADD     AX,BX
        PUSH    AX
        JMP     READ_CHAR
EVAL_MINUS:
        POP     AX
        POP     BX

        SUB     AX,BX
        PUSH    AX
        JMP     READ_CHAR
END_OF_SCAN:
        POP     BX
        MOV     CL,4
        MOV     AH,09H
        LEA     DX,NL
        INT     21H

NEXT_HEX:
        MOV     DL,BL
        AND     DL,0F0H
        SHR     DL,CL

        CMP     DL,9H
        JLE     ZERO_TO_9

        ADD     DL,37H
        JMP     DISPLAY
ZERO_TO_9:
        ADD     DL,30H
DISPLAY:
        MOV     AH,02H
        INT     21H
        SHL     BL,CL

         CMP     BL,0H
        JZ      EXIT
        JMP     NEXT_HEX
EXIT:
        MOV     AH,4CH
        INT     21H
MAIN    ENDP
END MAIN