Section 2: Registers31
keeping intermediate results in the stack above those being calculated. To lift information in the stack, you have used ENTER  and the automatic lift. To drop the stack, you have used the arithmetic functions. We will now consider the three remaining operations to move information in the stack.
 R  
Roll Up
 R  
Roll Down
 x y 
Exchange
     
     
You use these operations to verify (display) the contents of stack registers other than X and to move information into place for calculation.
  Notice that
  R  allows you to conveniently see t.
  R  saves x in the T-Register.
  x y allows you to look at y without altering t or z.
  R , R  and x y are functions appearing on the 9, 8, and 7 keys.
You may notice that R  and x y are also available on the D and E keys when the power is first turned on. The five functions shown in the window were selected because they are the most commonly used. Their primary intent is for manual use from the keyboard, as in this case. They each permit single keystroke operation of functions that otherwise would require two keystrokes. When the A , . . . , E keys are redefined by a program, the window functions are still available by two keystrokes.