About RPN history

[Voldemar]

Just found an interesting usage of Ans() command in RPN mode.
For example, fill stacks with 5 Enter 6 Enter 7 Enter 8 Enter. Then, for example, type 3 Enter. Now stacks looks like this:
5: 5
4: 6
3: 7
2: 8
1: 3
Then take command Ans() and type in brackets 1 (command Ans will execute for content of stack 1).
Press Enter and content off stack 3 stay on stack 1. Now stacks looks like this:
5: 5
4: 6
3: 7
2: 8
1: 7
Ans(1) works, do not work Ans(2), Ans(3)...