汇编语言中的While，Do While，For循环(emu8086)

问题描述

我想将高级语言中的简单循环转换为汇编语言(适用于emu8086)，例如，我有以下代码:

I want to convert simple loops in high-level languages into assembly language (for emu8086) say, I have this code:

 for(int x = 0; x<=3; x++)
 {
  //Do something!
 }

或

 int x=1;
 do{
 //Do something!
 }
 while(x==1)

或

 while(x==1){
 //Do something
 }

如何在emu8086中执行此操作?

How do I do this in emu8086?

推荐答案

For循环:

在C语言中循环:

For-loops:

For-loop in C:

for(int x = 0; x<=3; x++)
{
    //Do something!
}

8086汇编器中的相同循环:

The same loop in 8086 assembler:

        xor cx,cx   ; cx-register is the counter, set to 0
loop1   nop         ; Whatever you wanna do goes here, should not change cx
        inc cx      ; Increment
        cmp cx,3    ; Compare cx to the limit
        jle loop1   ; Loop while less or equal

如果您需要访问索引(cx)，则为循环.如果您只想进行0-3 = 4次操作，但又不需要索引，那会更容易:

That is the loop if you need to access your index (cx). If you just wanna to something 0-3=4 times but you do not need the index, this would be easier:

        mov cx,4    ; 4 iterations
loop1   nop         ; Whatever you wanna do goes here, should not change cx
        loop loop1  ; loop instruction decrements cx and jumps to label if not 0

如果您只想执行一个非常简单的指令一段恒定的时间，则还可以使用一个汇编程序指令，该指令将对该指令进行硬核化

If you just want to perform a very simple instruction a constant amount of times, you could also use an assembler-directive which will just hardcore that instruction

times 4 nop

循环执行

在C语言中执行循环操作

Do-while-loops

Do-while-loop in C:

int x=1;
do{
    //Do something!
}
while(x==1)

汇编程序中的相同循环:

The same loop in assembler:

        mov ax,1
loop1   nop         ; Whatever you wanna do goes here
        cmp ax,1    ; Check wether cx is 1
        je loop1    ; And loop if equal

循环时

在C中循环时

While-loops

While-loop in C:

while(x==1){
    //Do something
}

汇编器中的相同循环:

        jmp loop1   ; Jump to condition first
cloop1  nop         ; Execute the content of the loop
loop1   cmp ax,1    ; Check the condition
        je cloop1   ; Jump to content of the loop if met

对于for循环，您应该使用cx-register，因为它非常标准.对于其他循环条件，您可以记录自己的喜好.当然，请用您要在循环中执行的所有指令替换无操作指令.

For the for-loops you should take the cx-register because it is pretty much standard. For the other loop conditions you can take a register of your liking. Of course replace the no-operation instruction with all the instructions you wanna perform in the loop.

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