ds:si和es:di在汇编中意味着什么? [英] What do ds:si and es:di mean in assembly?

问题描述

movsb(移动字符串，字节)指令获取地址处的字节 ds:si，将其存储在地址es:di中，然后递增或递减 si和di寄存器加1.

The movsb (move string, bytes) instruction fetches the byte at address ds:si, stores it at address es:di, and then increments or decrements the si and di registers by one.

我知道esi，si和edi，di寄存器，

I know esi,si and edi,di registers,

但不是ds:si和es:di，

它们是什么意思?

推荐答案

ds:si和es:di表示相关寄存器所引用的segment:offset.当您在实模式下工作时(偏移最大为每个64K)，这尤其重要.

ds:si and es:di mean the segment:offset referred to by the registers in question. This is primarily important when you're working in real mode (where offsets are a maximum of 64K apiece).

在实模式下，将偏移的段组合为segment * 16 + offset.

In real mode, the segment are offset are combined as segment * 16 + offset.

在保护模式下，段寄存器包含一个选择器".选择器引用的内存的基地址与选择器本身的值并不直接相关，而是选择器仅充当在表中查找数据的索引.但是，在常规情况下，这意味着很少-大多数(当前)保护模式环境都使用CS，DS，ES和SS进行设置，而CS，DS，ES和SS均设置为基地址0且最大偏移量为4 GB，因此通过DS与ES寻址没有区别.

In protected mode, a segment register holds a "selector". The base address of the memory referred to by the selector isn't directly related to the value of the selector itself -- rather, the selector just acts as an index to look up data in a table. In the usual case, however, this means very little -- most (current) protected mode environments are set up with CS, DS, ES and SS all set up with base addresses of 0 and maximum offsets of 4 Gigabytes, so addressing via DS vs. ES makes no difference.

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