HP 35s HP 35s scientific calculator - User Guide - Page 219

Flags A flag is an indicator of status. It is either set (true) or clear (false). Testing a flag is another conditional test that follows the "Do if true" rule: program execution proceeds directly if the tested flag is set, and skips one line if the flag is clear. Meanings of Flags The HP 35s has 12 flags, numbered 0 through 11. All flags can be set, cleared, and tested from the keyboard or by a program instruction. The default state of all 12 flags is clear. The three-key memory clearing operation described in appendix B clears all flags. Flags are not affected by  Flags 0, 1, 2, 3, and 4 have no pre-assigned 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 . An overflow occurs when a 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. Besides, when using non-decimal bases in programs, flag 6 also gets set for in programs. 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 off by pressing , flag 7 is set or cleared as well. Programming Techniques 14-9