DM-42 and WP-43S

[Paul Dale]

The stack lift flag is a residual from the early days when there wasn't enough memory to allow the entry of a new number without destroying one of the registers. You were entering the number directly in the X register.

It isn't a bug, it is as designed and intended. It isn't the enter after the division that isn't causing the stack lift, it is the digit entry after the enter.

After the divide, the stack will contain 20 and the stack lift flag is set.
After the enter, the stack will contain 20 20 and the stack lift flag is clear.
After the 2, the stack will contain 20 2 (the 2 replaces the 20 because of the clear stack lift flag).
After the divide, the stack will contain 10 and the stack lift flag will be set.

The stack operation is logically consistent, just with a rule or two you weren't aware of. The system works well which is why people still want it. The number of operations that clear the stack lift flag are small: enter, %, sigma+, clx and each one makes sense preventing stack lift.

The 34S does have an input buffer which allows you to begin digit entry and backspace out without changing the stack but in all other ways it supports the stack lift flag's operation.


- Pauli