为什么我会溢出?(NASM汇编程序)

为了这个程序的目的,我必须制作一个程序来计算圆锥的体积,它是22/21*(r^2)*h。

所以我开发的这段代码适用于所有变量,这些变量相乘后不会导致EDX寄存器被填充。我不能将寄存器移位或“或”,也不能使用跳转或cmp语句。我还必须使用8位寄存器用于高度和宽度变量,16位用于半径^2和半径^2*高度计算,然后用32位完成最后的除法计算。看看吧。我不知道为什么它会溢出到EDX中,我也不知道如何纠正它。。。

.data

radius          WORD ?                                      ;var for radius
height          WORD ?                                      ;var for height
numerator       WORD 22                                     ;Making a variable for numerator
denominator     DWORD 21                                    ;Making a variable for denominator
volume          DWORD ?                                     ;Making a variable to store volume main
decimal         DWORD ?                                     ;Making a variable to store volume remainder
prompt BYTE "Enter the radius: ",0                          ;val for radius prompt
promp2 BYTE "Enter the height: ",0                          ;val for height prompt
result BYTE "The volume of the cone is: ", 0                ;val for printing volume
decim  BYTE ".", 0                                          ;val for decimal place

                                                                ;volume of cone is 1/3(pi(r^2)h) or 22/21(r^2)h

.code

main PROC
    mov edx,OFFSET promp2                                       ;move prompt into edx for printing
    call WriteString                                            ;ask user for height

    mov eax,0
    mov edx,0
    mov ecx,0
    mov ebx,0                                                   ;move zero into all main registers

    call ReadDec                                                ;reading the height
    mov bl,al                                                   ;move height into storage

    mov edx,OFFSET prompt                                       ;move promp2 into edx for printing
    mov eax,0                                                   ;re-zero eax
    call WriteString                                            ;ask user for radius
    call ReadDec

    mul al                                                      ;obtain r^2
    mul bl                                                      ;multiply r^2 by height
    mov edx,0                                                   ;zero out edx
    mov dx,numerator                                            ;move numerator into dx
    mul dx                                                      ;multiply r^2*h by 22

    mov ebx,denominator                                         ;move 21 into ebx to divide
    div ebx                                                     ;divide by 21 to get total volume
    mov volume,eax                                              ;move volume into volume variable
    mov decimal,edx                                             ;move decimal remainder into decimal variable

    mov edx,OFFSET result                                       ;prepare string result for printing
    call WriteString                                            ;print result string
    mov eax,volume                                              ;move volume into eax to print     
    call WriteDec                                               ;print volume
    mov edx,OFFSET decim                                        ;move dec into print register
    call WriteString                                            ;print decimal
    mov eax,decimal                                             ;move decimal remainder into eax to print
    call WriteDec                                               ;print decimal value
    call CRLF                                                   ;carriage return and new line
    call WaitMsg                                                ;pause output

    exit
main ENDP

也许我可以为中间运算做不同的寄存器,但考虑到当前的8-8-16-16-32要求,我不知道如何实现。如果有人能帮我找到一个有效的解决方案,并解释为什么它能起作用,也许可以逐步了解一下,这样我就可以理解为什么我的解决方案不能用于更大的整数(大多数超过20的整数不起作用),这将是一件令人惊讶的事情。提前感谢你能给我的任何帮助!