汇编除以零溢出

Question

对 8086 Assembly 相当陌生，我遇到了一个我似乎无法弄清楚的错误..

当第 4 位数字(例如 123X)为 0 或 1 时，div 过程(也许之前还有其他东西)给我带来错误，错误是除以零，它也并不总是适用于其他数字。

我需要做的是输入4位数字，确保输入正确，将4位数字相加，然后除以4位数字之和，如果没有余数，则为哈沙德数，然后需要检查特殊情况，4 位数字的翻转总和是否也有效。

例如数字1729，和是19，翻转后是91，两者都可以被1729整除，没有余数。这是我的代码...抱歉，如果太长...

; Harshad.asm - check if input from user (4 digits, 1000-9999) is a Harshad number and if so, check if it's a "special" Harshad number
;
    .MODEL SMALL
    .STACK 100h
    .DATA
RequestStr     DB 'Enter a 4 digit number (1000-9999):',13,10,'$'
IsHarshad      DB ' is a Harshad number.$',13,10
SpecialHarshad DB 13,10,'It is also a special Harshad number.',13,10,'$'
NotHarshad     DB ' is not a Harshad number$',13,10
IncorrectInput DB 13,10,'Input is incorrect.',13,10,'$'
Num            DW ? ;Will fit a "word" size (16 bits)
DigitSum       DB ? ;Sum of digits (maximum 9*4) fits a "byte" size (8 bits)
TEN            DB 10
Temp           DB ? ;Used to check if number is also special Harshad
;
     .CODE
     MOV AX,@DATA                ;DS can be written to only through a register
     MOV DS,AX                   ;Set DS to point to data segment
     MOV AH,9                    ;Set print option for INT 21h
     MOV DX,OFFSET RequestStr    ;Set  DS:DX to point to RequestString
     INT 21h                     ;Print RequestStr
    ;
NumberInput:
    ;First digit
    MOV AH,1        ;Set scanning (input) option for INT 21h
    INT 21h         ;Scan first digit
    SUB AL,'0'      ;Converting from ascii value to numeral value
    CMP AL,1        ;First digit must be between 1 and 9 in order for the number to be of 4 digits
    JB WrongInput   ;Otherwise jump to WrongInput label
    CMP AL,9
    JA WrongInput
    MOV DigitSum,AL ;Store only first digit's value at the variable DigitSum
    MOV AH,0        ;Set AH to zero so it won't affect the answer
    MUL TEN         ;multiply AX by 10
    MOV Num,AX
    ;Second digit
    MOV AX,0
    MOV AH,1 
    INT 21h
    SUB AL,'0'
    CMP AL,0
    JB WrongInput
    CMP AL,9
    JA WrongInput
    MOV AH,0
    ADD DigitSum,AL ;Add only second's digit value to DigitSum
    ADD Num,AX      ;Add AX's value (which has been multiplied by 10 with the first digit) to Num variable
    MOV AX,0
    MOV AX ,Num     ;Move new Num's value to AX to multiply it by 10
    MUL TEN
    MOV Num,AX
    ;Third digit
    MOV AX,0
    MOV AH,1
    INT 21h
    SUB AL,'0'
    CMP AL,0
    JB WrongInput
    CMP AL,9
    JA WrongInput
    ADD DigitSum,AL
    MOV AH,0
    ADD Num,AX
    MOV AX,0
    MOV AX,Num
    MUL TEN
    MOV Num,AX
    ;Forth digit
    MOV AX,0
    MOV AH,1 
    INT 21h
    SUB AL,'0'
    CMP AL,0
    JB WrongInput
    CMP AL,9
    JA WrongInput
    ADD DigitSum,AL ;Now DigitSum contains the sum of each of the 4 digits in the number
    MOV AH,0
    ADD Num,AX ;Num contains full 4 digits number
    JMP CheckHarshad    
WrongInput:      
    MOV AH,9
    MOV DX,OFFSET IncorrectInput
    INT 21h
    JMP CodeEnd
CheckHarshad:
    MOV AX,0
    MOV AX,Num
    DIV DigitSum ;Number will be stored in AL and the remainder in AH
    CMP AH,0 ;Check if there is remainder or not
    JE CheckSpecialHarshad
    MOV AH,9
    MOV DX,OFFSET NotHarshad 
    INT 21h
    JMP CodeEnd
CheckSpecialHarshad:
    MOV AH,9
    MOV DX, OFFSET IsHarshad
    INT 21h
    MOV AX,0
    MOV AL,DigitSum
    DIV TEN
    MOV Temp,AL
    MOV DigitSum,AH
    MOV AX,0
    MOV AL,DigitSum
    MUL TEN
    ADD AL,Temp
    MOV DigitSum,AL ;DigitSum now has it's former number flipped
    MOV AX,0
    MOV AX,Num
    DIV DigitSum
    CMP AH,0
    JNE CodeEnd
    MOV DX,OFFSET SpecialHarshad
    MOV AH,9
    INT 21h
CodeEnd:
    MOV AH,4Ch
    INT 21h
    END

Answer 1

在 @Jester 的帮助下，我更改了一些值，这是最终结果(汇编代码，检查 4 位数字是否是 Harshad 数字，如果是，还检查它是否是特殊的 Harshad 数字):

; Harshad.asm - check if input from user (4 digits, 1000-9999) is a Harshad number and if so, check if it's a "special" Harshad number
;
    .MODEL SMALL
    .STACK 100h
    .DATA
RequestStr     DB 'Enter a 4 digit number (1000-9999):',13,10,'$'
IsHarshad      DB ' is a Harshad number.',13,10,'$'
SpecialHarshad DB 'It is also a special Harshad number.',13,10,'$'
NotHarshad     DB ' is not a Harshad number',13,10,'$'
IncorrectInput DB 13,10,'Input is incorrect.',13,10,'$'
Num            DW ? ;Will fit a "word" size (16 bits)
DigitSum       DW ? ;Sum of digits
TEN            DW 10
TENbyte        DB 10
Temp           DB ? ;Used to check if number is also special Harshad during the div process
Temp2          DB ? ;Used with special Harshad div process  
;
     .CODE
     MOV AX,@DATA                ;DS can be written to only through a register
     MOV DS,AX                   ;Set DS to point to data segment
     MOV AH,9                    ;Set print option for INT 21h
     MOV DX,OFFSET RequestStr    ;Set DS:DX to point to RequestString
     INT 21h                     ;Print RequestStr
;
NumberInput:
    ;First digit
    MOV AH,1        ;Set scanning (input) option for INT 21h
    INT 21h         ;Scan first digit
    MOV DX,0
    SUB AL,'0'      ;Converting from ascii value to numeral value
    CMP AL,1        ;First digit must be between 1 and 9 in order for the number to be of 4 digits
    JB WrongInput   ;Otherwise jump to WrongInput label
    CMP AL,9
    JA WrongInput
    MOV AH,0
    MOV DigitSum,AX ;Store only first digit's value at the variable DigitSum
    MUL TEN         ;Multiply AX by 10
    MOV Num,AX
    ;Second digit
    MOV AX,0
    MOV AH,1 
    INT 21h
    SUB AL,'0'
    CMP AL,0
    JB WrongInput
    CMP AL,9
    JA WrongInput
    MOV AH,0
    ADD DigitSum,AX ;Add only second's digit value to DigitSum
    ADD Num,AX      ;Add AX's value (which has been multiplied by 10 with the first digit) to Num variable
    MOV AX,0
    MOV AX,Num      ;Move new Num's value to AX to multiply it by 10
    MUL TEN
    MOV Num,AX
    ;Third digit
    MOV AX,0
    MOV AH,1
    INT 21h
    SUB AL,'0'
    CMP AL,0
    JB WrongInput
    CMP AL,9
    JA WrongInput
    MOV AH,0
    ADD DigitSum,AX
    ADD Num,AX
    MOV AX,0
    MOV AX,Num
    MUL TEN
    MOV Num,AX
    ;Forth digit
    MOV AX,0
    MOV AH,1 
    INT 21h
    SUB AL,'0'
    CMP AL,0
    JB WrongInput
    CMP AL,9
    JA WrongInput
    MOV AH,0
    ADD DigitSum,AX ;Now DigitSum contains the sum of each of the 4 digits in the number
    ADD Num,AX ;Num contains full 4 digits number
    JMP CheckHarshad    
WrongInput:      
    MOV AH,9
    MOV DX,OFFSET IncorrectInput
    INT 21h
    JMP CodeEnd
CheckHarshad:
    MOV AX,0
    MOV DX,0
    MOV AX,Num
    DIV DigitSum ;Number will be stored in AX and the remainder in DX
    CMP DX,0 ;Check if there is remainder or not
    JE CheckSpecialHarshad
    MOV AH,9
    MOV DX,OFFSET NotHarshad 
    INT 21h
    JMP CodeEnd
CheckSpecialHarshad:
    MOV AH,9
    MOV DX, OFFSET IsHarshad
    INT 21h
    MOV AX,0
    MOV AX,DigitSum
    DIV TENbyte
    MOV Temp,AL
    MOV Temp2,AH
    MOV AX,0
    MOV AL,Temp2
    MUL TENbyte
    ADD AL,Temp
    MOV Temp2,AL ;Temp2 now has the DigitSum number flipped
    MOV AX,0
    MOV AX,Num
    DIV Temp2
    CMP AH,0
    JNE CodeEnd
    MOV DX,OFFSET SpecialHarshad
    MOV AH,9
    INT 21h
CodeEnd:
    MOV AH,4Ch
    INT 21h
    END