Appendix C: Stack Lift And Last X - HP -33E Owner's Handbook Manual

Appendix C
Stack Lift and LAST X
Your calculator has been designed to operate in a natural, normal
manner. As you have seen as you worked through this handbook, you
are seldom required to think about the operation of the automatic memory
stack—you merely work through calculations in the same way you
would with a pencil and paper, performing one operation at a time.
There may be occasions, however, particularly as you program the
calculator, when you wish to know the effect of a particular operation
upon the stack. The following explanation and table should help you.
Digit Entry Termination
Most operations on the calculator, whether executed as instructions in a
program or pressed from the keyboard, terminate digit entry. This means
that the calculator knows that any digits you key in after any of these
operations are part of a new number.
Stack Lift
There are three types of operations on the calculator, depending upon
how they affect the stack lift. These are stack disabling operations,
stack enabling operations and neutral operations.
Disabling Operations
There are only four stack disabling operations on the calculator. These
operations disable the stack lift, so that a number keyed in after one of
these disabling operations writes over the current number in the
displayed X-register and the stack does not lift. These special disabling
operations are:
Enabling Operations
The bulk of the operations on the keyboard, including one- and two-
number mathematical functions like and (], are stack enabling
operations. These operations enable the stack lift, so that a number keyed
in after one of the enabling operations lifts the stack.
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