What are CLD and STD for in x86 assembly language? What does DF do?

Question

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

Answer 1

If using Windows, then as per the STDCALL calling convention -

Under STDCALL, the direction flag is clear on entry and must be returned clear.

So if you set DF, then before an API call you must clear it.