HP 35s Scientific Calculator - Manual (Page 70)

3-6 Storing Data into Variables
To leave the VAR catalog at any time, press either  or  . An alternate
method to clearing a variable is simply to store the value zero in it. Finally, you can
clear all direct variables by pressing   (). If all direct
variables have the value zero, then attempting to enter the VAR catalog will display
the error message “   ”.
If the value of a variable has too many digits to display completely, you can use
Õ and Ö to view the missing digits.
Arithmetic with Stored Variables
Storage arithmetic and recall arithmetic allow you to do calculations with a
number stored in a variable without recalling the variable into the stack. A
calculation uses one number from the X–register and one number from the
specified variable.
Storage Arithmetic
Storage arithmetic uses  ,  ,  , or 
 to do arithmetic in the variable itself and to store the result there. It uses the
value in the X–register and does not affect the stack.
New value of variable = Previous value of variable {+, –, Ч, ч} x.
For example, suppose you want to reduce the value in A(15) by the number in the
X–register (3, displayed). Press
A . Now A = 12, while 3 is still in
the display.