HP (Hewlett-Packard) F2215AA#ABA ユーザーズマニュアル

The X and Y–Registers are what you see except when a menu, a message, an 
equation line ,or a program line is being displayed. You might have noticed that 
several function names include an x or y.

This is no coincidence: these letters refer to the X– and Y–registers. For example, 



 



 raises ten to the power of the number in the X–register.

Pressing 





() always clears the X–register to zero; it is also used to 

program this instruction. The 



 key, in contrast, is context–sensitive. It either clears 

or cancels the current display, depending on the situation: it acts like 



1

() only when the X–register is displayed. 



 also acts like 





() when the X–register is displayed and digit entry is terminated 

(no cursor present). 

The 



 (roll down) key lets you review the entire contents of the stack by 

"rolling" the contents downward, one register at a time. You can see the numbers 
as they roll through the x- and y-registers.

Suppose the stack is filled with 1, 2, 3, 4. (press 



) Pressing 



 four times rolls the numbers 

all the way around and back to where they started:

1

 

 

4

 

3

 

2

1

2

 

 

1

4

 

3

2

3

 

 

2

1

 

4

3

4

 

3

2

 

1

4