HP 33s User Manual page 193

Flags 0, 1, 2, 3, and 4 have no preassigned meanings. That is, their
states will mean whatever you define them to mean in a given program. (See
the example below.)
Flag 5, when set, will interrupt a program when an overflow occurs within
the program, displaying  and
result exceeds the largest number that the calculator can handle. The largest
possible number is substituted for the overflow result. If flag 5 is clear, a
program with an overflow is not interrupted, though  is displayed
briefly when the program eventually stops.
Flag 6 is automatically set by the calculator any time an overflow occurs
(although you can also set flag 6 yourself). It has no effect, but can be tested.
Flags 5 and 6 allow you to control overflow conditions that occur during a
program. Setting flag 5 stops a program at the line just after the line that
caused the overflow. By testing flag 6 in a program, you can alter the
program's flow or change a result anytime an overflow occurs.
Flags 7, 8 and 9 control the display of fractions. Flag 7 can also be
controlled from the keyboard. When Fraction–display mode is toggled on or
¹ É
off by pressing
Flag
Status
Clear Fraction display
off; display real
(Default)
numbers in the
current display
format.
Set Fraction display
on; display real
numbers as
fractions.
, flag 7 is set or cleared as well.
Fraction–Control Flags
7
Fraction
denominators not
greater than the
/c value.
Fraction
denominators are
factors of the /c
Value.
â
. An overflow occurs when a
8
Reduce fractions
to smallest form.
No reduction of
fractions. (Used
only if flag 8 is
set.)
Programming Techniques
9
13–9