装配程序的两位和三位数容量

Question

到目前为止，这是我的汇编代码。它只处理一位数的容量。我刚刚开始使用子程序，所以我遇到了一些麻烦。我如何添加两位数输入和三位输出容量？ （附件）

; Filename SubTest3.asm

; This program is designed to demonstrate the use of subroutines in
; programming. 
; This file is phase 3 and introduces a multiply subroutine.
; Current support subroutines include : PMPTOUT, MULT, ATOI, ITOA

        .ORIG   x3000       ; load the program here

; Request factor1 from the user
; To be retrieved from R0 according to convention

        AND     R0,R0,#0

; Call prompt subroutine and output PROMPT1

        LEA R3,PROMPT1
        JSR PMPTOUT

        TRAP    x20     ; Use GETC to retrieve user character entry into R0
        TRAP    x21     ; Echo the entered factor

; Convert factor1 to an integer
; Use R2 to convert ASCII factor1 to an integer, store in R4 when done

        AND R2,R2,#0    ; Clear R2
        ADD R2,R0,#0    ; Load R2 with the ASCII value of factor1
        JSR ATOI
        ADD R4,R4,R2

        LD  R0,NewLine  ; Go to a clean line for the next input
        TRAP    x21

; Request factor2 from user
; To be retrieved from R0 according to convention

        AND R0,R0,#0

; Call prompt subroutine and output PROMPT2

        LEA R3,PROMPT2
        JSR PMPTOUT

        TRAP    x20     ; Use GETC to retrieve user character entry into R0
        TRAP    x21     ; Echo the entered factor

; Convert factor2 to an integer
; Use R2 to convert ASCII factor2 to an integer, store in R5 when done

        AND R2,R2,#0    ; Clear R2
        ADD R2,R0,#0    ; Load R2 with the ASCII value of factor1
        JSR ATOI
        ADD R5,R5,R2

        LD  R0,NewLine  ; Go to a clean line for the next input
        TRAP    x21

; Perform multiplication with MULT subroutine
; Registers R4 and R5 correctly contain two integer factors here.
; R6 contains the integer product.

        JSR MULT

; Use prompt writing subroutine to announce result

        LEA R3,RESULT
        JSR PMPTOUT

; Display the result of the multiplication on a clean line

        JSR ITOA
        TRAP    x21     ; Write the product to the display
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
        TRAP x25        ; HALT the processor
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
PMPTOUT     ST  R7,SaveR7
        AND     R0,R0,#0
        ADD     R0,R3,R0
        TRAP    x22     ; Call PUTS
        LD  R7,SaveR7
        RET
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Multiply subroutine
; Expects factor1 in R4 and factor2 in R5
; Returns the product in R6

MULT        AND R6,R6,#0    ; Clear R6 to hold result of multiplication
AGAIN       ADD R6,R6,R4
        ADD R5,R5,#-1   
        BRp AGAIN
        RET
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Subroutine to convert ASCII character to an integer
; This routine uses R2 as a holding register for the correction
ATOI        ST  R3,SaveR3
        AND R3,R3,#0    ; Clear R3
        LD  R3,ASCII    ; Load ASCII correction into R3
        NOT R3,R3       ; Form 1s complement
        ADD R3,R3,#1    ; Form 2s complement
        ADD R2,R2,R3    ; ACSII correction, R2 now contains integer for
                    ; math operations
        LD  R3,SaveR3
        RET
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;
ITOA        ST  R3,SaveR3
        AND R0,R0,#0    ; Clear R0 for product display
        ADD R0,R6,R0    ; Load product integer into R0
        AND R3,R3,#0    ; Clear R3 to ready ASCII correction 
        LD  R3,ASCII    ; Load ASCII correction into R3
        ADD R0,R0,R3    ; Make integer an ASCII character for output
        LD  R3,SaveR3
        RET
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; MEMORY AREA

NewLine     .FILL       x000A
ASCII       .FILL       x0030
SaveR7      .FILL       x0000
SaveR3      .FILL       x0000
PROMPT1     .STRINGZ    "Enter the first factor\n"
PROMPT2     .STRINGZ    "Enter the second factor\n"
RESULT      .STRINGZ    "The product of the factors is :\n"

        .END
; End of