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wrnum:

push si

push dx

push cx

push ax

mov si,num_buf

; extended precision division from section 9.3.5

; of Randall Hyde's "Art of Assembly"

; start: DX=dividend MSW, AX=dividend LSW, BX=divisor

wrnum1:

push ax

mov ax,dx

xor dx,dx

; before div: DX=0, AX=dividend MSW, BX=divisor

; after div: AX=quotient MSW, DX=intermediate remainder

div bx

mov cx,ax

pop ax

; before div: DX=intermediate remainder, AX=dividend LSW, BX=divisor

; after div: AX=quotient LSW, DX=remainder

div bx

; end: DX=quotient MSW, AX=quotient LSW, CX=remainder

xchg dx,cx

add cl,'0'

cmp cl,'9'

jbe wrnum2

add cl,('A'-('9'+1))

wrnum2:

dec si

mov [si],cl

mov cx,ax

or cx,dx

jne wrnum1

call cputs

pop ax

pop cx

pop dx

pop si

ret

下面是解释:

hi, first of all, the code snippet you have given is doing only the printing the 32-bit number in a specified radix. its not part of any memory detection routine. i think you havent’t completely gone through the comments given along with the code.

its just dividing the number with the radix, each time getting the least significant number, converting to printable ascii format in the range ’0′ – ’9′ and ‘A’ – ‘Z’ (though not limited to ‘Z’), storing the result in the reverse order starting from the address num_buf(you can notice a 40 bytes array declared just above the address) and after the conversion is over cputs is called to print the formed string.

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