Appendix B: Stack Lift and the LAST X Register 211

T

y

 

y

 

y

 

y

 

 

 

 

 

 

 

 

Z

x

 

x

 

x

 

x

Y

 

 

 

 

 

 

 

4.0000

 

53.1301

 

53.1301

 

53.1301

X

 

 

 

 

 

 

 

3

 

5.0000

 

0.0000

 

7

 

 

 

 

 

 

 

 

Keys:

:

`

7

 

 

 

 

Stack

 

Stack

 

No stack

 

 

 

enabled.

 

disabled.

 

lift.

Imaginary X-Register.All enabling functions provide for a zero to be placed in the imaginary X-register when the next number is keyed or recalled into the display.

Neutral Operations

Stack Lift. Some operations, like •, are neutral; that is, they do not alter the previous status of the stack lift. Thus, if you disable the stack lift by pressing v, then press ´•n and key in a new number, that number will write over the number in the X-register and the stack will not lift. Similarly, if you have previously enabled the stack lift by executing, say ¤, then execute a • instruction followed by a digit entry sequence, the stack will lift.*

The following operations are neutral on the HP-15C:• g U ¦it“nnn CLEAR u ¥

^

‚

CLEAR Q %†

D

Â

CLEAR ∑

R

W

©

Imaginary X-Register.The above operations are also neutral with respect to clearing the imaginary X-register.

*All digit entry functions are also neutral during digit entry. After digit entry termination, “and ‛ are lift enabling, −is disabling.

†That is, the ´%sequence used to view the imaginary X-register.