问题描述
我正试图得到这样的东西
*
***
*****
*******
*********
***
***
我已经学会了如何创建一个循环，并尝试使同一代码多次使用该循环，但是失败了。以下是我到目前为止编写的代码
[BITS 16]
[ORG 0x7C00]
top:
;; Put 0 into ds (data segment)
;; Can't do it directly
mov ax,0x0000
mov ds,ax
;; si is the location relative to the data segment of the
;; string/char to display
mov si,fourSpace
call writeString
mov ch,1 ; mov 1 into the register ch
call dotsLoop
mov si,threeSpace
call writeString
mov ch,3 ; mov 3 into the register ch
call dotsLoop
mov si,twoSpace
call writeString
mov ch,5 ; mov 5 into the register ch
call dotsLoop
mov si,onespace
call writeString
mov ch,7 ; mov 7 into the register ch
call dotsLoop
mov ch,9 ; mov 9 into the register ch
call dotsLoop
mov si,branchThreeSpace1
call writeString
mov ch,branchThreeSpace2
call writeString
mov ch,3 ; mov 3 into the register ch
call dotsLoop
jmp $ ; Spin
dotsLoop:
mov si,dot ; print the dot
call writeString ; See below
dec ch ; reduce what is in ch by 1
cmp ch,0 ; compare to see if what is store in ch is 0
jne dotsLoop ; if ch does not contain 0 call dotsLoop again.
mov si,cr ; print the newline code
call writeString ; See below
ret ; when ch contains 0 return back to main code
writeString:
mov ah,0x0E ; display a chacter (as before)
mov bh,0x00
mov bl,0x07
nextchar:
Lodsb ; Loads [SI] into AL and increases SI by one
;; Effectively "pumps" the string through AL
cmp al,0 ; End of the string?
jz done
int 0x10 ; BIOS interrupt
jmp nextchar
done:
ret
fourSpace db ' ',0 ; For spacing
1dot db '*',13,10,0
threeSpace db ' ',0 ; For spacing
3dot db '*',0
twoSpace db ' ',0 ; For spacing
5dot db '*',0
onespace db ' ',0 ; For spacing
7dot db '*',0
9dot db '*',0
branchThreeSpace1 db ' ',0 ; For spacing
branchdot1 db '*',0
branchThreeSpace2 db ' ',0 ; For spacing
branchdot2 db '*',0
times 510-($-$$) db 0
dw 0xAA55
但是，正如预期的那样，我在这些行的开头出现了 标签或指令 错误
1dot db '*',0
3dot db '*',0
etc..
有人可以指导我如何在多个实例中使用dotsLoop吗？
解决方法
1dot db '*',13,10,0 3dot db '*',0 5dot db '*',0 7dot db '*',0 9dot db '*',0 branchdot1 db '*',0 branchdot2 db '*',0
就像Michael Petch在评论中写道，NASM标签不能以数字0-9开头。
接下来，由于所有这些行都具有相同的内容，因此您无需重复7次。 CH寄存器将满足您的所有需求。
此外，为了在程序中正确操作，您需要从行中删除该回车符和换行符。
这就是剩下的：
dot db '*',0
fourSpace db ' ',0 ; For spacing threeSpace db ' ',0 ; For spacing twoSpace db ' ',0 ; For spacing oneSpace db ' ',0 ; For spacing branchThreeSpace1 db ' ',0 ; For spacing branchThreeSpace2 db ' ',0 ; For spacing
在这里，您要重复6次！同样重要的是，您没有输出所需的空格数！每次您写4个空格，都不会产生圣诞树。
您可能需要的只是：
fourSpace db ' '
threeSpace db ' '
twoSpace db ' '
oneSpace db ' ',0
threeSpace 和 branchThreeSpace1 或 branchThreeSpace2 之间确实没有区别。它们都应该精确输出3个空格字符。
有人可以指导我如何在多个实例中使用dotsLoop吗？
将以上内容应用于您的代码，您将看到它可以正常工作：
...
mov si,fourSpace
call writeString
mov ch,1
call dotsLoop
mov si,threeSpace
call writeString
mov ch,3
call dotsLoop
mov si,twoSpace
call writeString
mov ch,5
call dotsLoop
mov si,oneSpace
call writeString
mov ch,7
call dotsLoop
mov ch,9
call dotsLoop
mov si,3
call dotsLoop
jmp $
dotsLoop:
...
writeString:
...
dot db '*',0
fourSpace db ' '
threeSpace db ' '
twoSpace db ' '
oneSpace db ' ',0
cr 13,0
...