什么是之间和QUOT的差异; CLD＆QUOT;和＆QUOT;性病QUOT;在汇编语言指令？ [英] What's the difference between "CLD" and "STD" instructions in assembly language?

问题描述

好了，我知道，CLD清方向标志和STD设置方向标志。
但什么是在设置和清除方向标志意义呢？

well, I know that CLD clears direction flag and STD sets direction flag. but what's the point in setting and clearing direction flag?

推荐答案

该方向标志被用来影响其中的 REP preFIX。还有一些由这个标志直接影响指令，例如 MOVS ， LODS ，中汽南方，和许多其他。

The direction flag is used to influence the direction in which some of the instructions work when used with the REP prefix. There is a number of instructions that are influenced by this flag directly, for example MOVS, LODS, SCAS, and many others.

在简单地说，当方向标志为0，说明通过增加数据指针每次迭代后（直到 ECX 工作为零或其他一些条件，视 REP preFIX），而如果该标志为1时，指针减

In a nutshell, when the direction flag is 0, the instructions work by incrementing the pointer to the data after every iteration (until ECX is zero or some other condition, depending on the flavour of the REP prefix), while if the flag is 1, the pointer is decremented.

这篇关于什么是之间和QUOT的差异; CLD＆QUOT;和＆QUOT;性病QUOT;在汇编语言指令？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！