HP 35s Scientific Calculator - Manual (Page 304)

B-4 User Memory and the Stack
Memory may inadvertently be cleared if the calculator is dropped or if power is
interrupted.
The Status of Stack Lift
The four stack registers are always present, and the stack always has a stack–lift
status. That is to say, the stack lift is always enabled or disabled regarding its
behavior when the next number is placed in the X–register. (Refer to chapter 2, "The
Automatic Memory Stack.")
All functions except those in the following two lists will enable stack lift.
Category CLEAR ALL MEMORY CLEAR
(Default)
Angular mode Unchanged Degrees
Base mode Unchanged Decimal
Contrast setting Unchanged Medium
Decimal point Unchanged ““
Thousand separator Unchanged “1,000”
Denominator (/c value) Unchanged 4095
Display format Unchanged FIX 4
Flags Unchanged Cleared
Complex mode Unchanged xiy
Fraction–display mode Unchanged Off
Random–number seed Unchanged Zero
Equation pointer EQN LIST TOP EQN LIST TOP
Equation list Cleared Cleared
FN = label Null Null
Program pointer PRGM TOP PRGM TOP
Program memory Cleared Cleared
Stack lift Enabled Enabled
Stack registers Cleared to zero Cleared to zero
Variables Cleared to zero Cleared to zero
Indirect Variables Not defined Not defined
Logic Unchanged RPN