Got it, as a newbie, I really like these things. They are very basic but crucial for our learning. Only by thoroughly mastering these basic things can we possibly write batch scripts. I hope the experts will write more such basic posts in the future, like issues about symbols, format issues, set syntax, etc. Some basic knowledge, although simple, without the guidance of experts, it's like a layer of window paper that no one pokes. No matter how simple it is, it's hard for newbies to break through. We should still lay a solid foundation, be clear like this. Looking forward to such posts!