FIF: creates a "Foot-Inch-Fraction mode" similar to the built-in
polar mode.  By Joe Horn.


INSTALLATION: FIF is a directory containing 4 programs:

    FKEY - starts FIF mode on level 1, with FIF softkeys.
    FEET - one-shot display routine used by FKEY.

    FK2 - starts FIF mode in status area, with FIF softkeys.
    FT2 - one-shot display routine used by FK2.

Just load FIF into memory and enter the directory.

If you wish, you may copy these programs into the HOME directory, and
then they will be available at all times.  If you only find yourself
using one pair of programs, feel free to purge the other pair.


GUIDED TOUR:

(1) FKEY

  Press FKEY.  See FT, IN, /2, /4, /8, and /16 softkeys (press NXT and
  see the EXIT softkey).  Press 1 FT and see 1' 0" displayed on level
  1 of the stack.  Press 3 / (the normal "divide" key) and see 0' 4"
  (one third of a foot). Press 7 IN and see 7 inches added to it: 0'
  11'. Press 15 /16 (the softkey) and see 15 16ths of an inch added to
  it: 0' 11" 15/16 . Press 1.75 + and see 1.75 feet added to it: 2' 8"
  15/16.  Press 4 * and see it multiplied by 4: 10' 11" 3/4.  Press 16
  +/- IN and see 16 inches subtracted from it: 9' 7" 3/4.  Perform any
  math you like; the answer is automatically displayed in FIF format
  on level 1. Press ON to see the measurement in decimal format, and
  press EVAL (or perform any math) to return to FIF format. Press NXT
  EXIT to exit FIF mode.

(2) FEET

  Press 8 1/X FEET.  See 0' 1" 1/2 (one eigth of a foot) displayed on
  level 1.  Perform any math you wish on this number (or press ON),
  and it returns to decimal format.  That's all that FEET does: it's a
  one-shot FIF display of whatever is on level 1.  It does not launch
  any sort of "mode" and so you don't have to "exit" from it.  Having
  FEET assigned to a key is handy when you just want to see the FIF
  form of a single number without launching FIF mode.

(3) FK2

  Now try FK2.  Use it exactly as you used FKEY, described above.  The
  only difference is that the FIF display is not on level 1, but in
  the status area.  Some people like it better this way, because you
  can see the decimal format on level 1, and the FIF format in the
  status area, simultaneously.  Press EXIT to exit FIF mode.

(4) FT2

  Try using FT2 exactly like FEET, described above.  Again, the only
  difference is where the FIF formatted number is displayed.


FINE POINTS:

The FT softkey merely does an ENTER, so you may press the ENTER key
instead of FT if you wish.  The IN, /2, /4, /8, and /16 softkeys, on
the other hand, always perform an addition, so if you want to enter a
measurement less than 1 foot, be sure to first press 0 FT (or 0
ENTER).

FKEY and FK2 turn on USER mode and require it to be on to work
properly, even though they do not create nor require any key
assignments.  They both turn off USER mode when you press the FIF-mode
EXIT softkey.  If this is not desired, remove the -62 CF from FKEY and
FK2, near the middle of each program.  They also create a variable in
the current directory called 'áENTER' (looks like BENT in the VAR
menu) which is also required for them to work properly.  It is
automatically purged when you press the FIF-mode EXIT softkey.
Finally, they also set system flag -63, the vectored-ENTER flag, and
clear it when exiting FIF mode.

FIF mode does nothing when anything other than a number is on level 1
of the stack, and it never has any effect on any other levels of the
stack.

Accuracy: Measurements are displayed to the nearest 16th of an inch,
with any necessary rounding propagating upwards into the inches, then
the feet.  Thus the displayed measurement is guaranteed to be the
closest FIF representation possible (to the nearest 16th of an inch)
as long as the measurement is of reasonable size, namely, less than
approximately the diameter of the earth.  (Space travel is not usually
measured in 16ths of an inch!)

Measurements are always positive.  That's why subtracting 2 feet from
1' 2" 3/4 gives an answer of 0' 9" 1/4 (the absolute value of the
expected negative answer).  FIF mode has no provisions for negative
measurements, so pressing +/- on a measurement has no effect.

These programs are 100% User RPL, and can be easily edited.  Leave the
SYSEVAL arguments alone, however.  Some engineers prefer a display
like 3' 12-1/4" instead of 3' 12" 1/4.  That would be an easily-made
change to the FEET and FT2 programs, and is left as an exercise for
the student.

A similar program called DMS, which puts the HP48 into a similar
"Degree-minutes-seconds mode", is also on this Goodies Disk.