HP HP-67 User Manual

256 Flags
Command-Cleared Flags
There are two types of flags. Flags FO and F1 are command-cleared
flags—that is, once they have been set by an @3 (sF) 0 or 3 [sF] 1
operation, they remain set until they are commanded to change by the
03 0 or @ 1 operations. Command-cleared flags are generally
used to remember program status (e.g., are outputs desired?).
Test-Cleared Flags
Flags F2 and F3 are test-cleared flags. They are cleared by a test
operation. For example, if you had set flag F2 with an [ (SF| 2 opera-
tion and then it was tested later in a program with an ([} 2 instruc-
tion, flag F2 would be cleared by the test—execution would continue
with the next step of program memory (the ‘DO if TRUE rule),
but the flag would then be cleared and would remain cleared until it
was set again. The test-cleared flags are used to save the 3
operation after a test. (However, test-cleared flags can be cleared by
the 03 operation, if desired.)
Besides being a test-cleared flag, flag F3 alone is set by digit
entry—that is, as soon as you key in a number from the keyboard,
flag F3 is set. It is also set when the magnetic card reader is used
to load data into the storage registers from a card. Even though you
do not test or use flag F3 in a program, it is nevertheless set by
digit entry from the keyboard or data loading from the magnetic card
reader.
All flags are cleared when the HP-67 is first turned ON or when
o is pressed in W/PRGM mode.
Now look at the way these flags can be used in programs.
Example: The following program contains an infinite loop that
illustrates the operation of a flag. (In this case, the flag used is
command-cleared flag FO.) The program alternately displays all 1’s
and all 0’s by changing the status of the flag, and hence, the result
of the test in step 007, each time through the loop. A flowchart for
the simple program might look like this:

HP HP-67 Specifications

General

Brand	HP
Model	HP-67
Category	Calculator
Language	English