HP 33s Scientific manual Last X Register

„During program entry, bdeletes the currently–displayed program line and ‡cancels program entry.

„During digit entry, bbackspaces over the displayed number.

„If the display shows a labeled number (such as /)), pressing ‡ or bcancels that display and shows the X–register.

„When viewing an equation, bdisplays the cursor at the end the equation to allow for editing.

„During equation entry, bbackspaces over the displayed equation, one function at a time.

For example, if you intended to enter 1 and 3 but mistakenly entered 1 and 2, this is what you should do to correct your error:

T

Z

Y

X

1

1

2

1

1

1

2

34

1

0

1

3

5

1.Lifts the stack

2.Lifts the stack and replicates the X–register.

3.Overwrites the X–register.

4.Clears x by overwriting it with zero.

5.Overwrites x (replaces the zero.)

The LAST X Register

The LAST X register is a companion to the stack: it holds the number that was in the X–register before the last numeric function was executed. (A numeric function is an operation that produces a result from another number or numbers, such as #.) Pressing {returns this value into the X–register.

This ability to retrieve the "last x" has two main uses:

1.Correcting errors.

RPN: The Automatic Memory Stack 2–7