akcs.aaron@hpcvbbs.UUCP (Aaron Boonshoft) (04/22/91)
%%HP: T(3)A(R)F(.);
DIR
@ Hi, I recently graduated from The Ohio State University and moved to
@ Corvallis Oregon to pursue a career in handheld computing. As I
@ learn more about programming these devices, I have come to realize some
@ things about user interfaces. The following summarizes some of what I
@ have learned. I hope it is helpful.
@*********************************************************************
@ +===========================+
@ | HP48 SCIENTIFIC EXPANDABLE|
@ A |+-------------------------+| Hi! How are you?
@ || <( O )> <( O )> ||
@ || || /
@ FRIENDLY || [ ] [ ] || ______/
@ || [ ][ ] [ ][ ] ||
@ |+-------------------------+|
@ HP 48 |===========================|
@ || [A] [B] [C] [D] [E] [F] ||
@ || MTH PRG CST VAR [^] NXT ||
@ USER || ['] STO EVL [<] [v] [>] || by
@ || SIN COS TAN SQR Y^X 1/X ||
@ || [ENTER] +/- EEX DEL [<= ||
@ INTER- || [a] [7] [8] [9] [/] || Aaron Boonshoft
@ || [<] [4] [5] [6] [X] ||
@ || [>] [1] [2] [3] [-] ||
@ FACE || [ON [0] [.] SPC [+] ||
@ +===========================+
@ Introduction:
@ One of the more challenging aspects of writing professional software
@ for the HP 48 is the user interface. Professional software normally
@ requires a very clean, friendly, and flexible user interface.
@ The software should not generate an error regardless of the keys the
@ user presses (including [ATTN]) or of the input data the user enters
@ (including total gibberish). The user interface is often time
@ consuming to design and debug. It may also account for more
@ than half of the code in a project. One way of combating the
@ problems of writing user interface code is to write the code in the
@ form of subprograms (programs designed to be used by other
@ programs). In this form, the code may be used for many different
@ projects. This may greatly reduce their size and development time.
@ Below are five sets of programs and subprograms. The first set
@ just contains examples of how the other four are used. Each of the
@ other four contain one major subprogram which, in some cases, uses
@ the help of supporting subprograms or other major subprograms. The
@ subprograms take care of some general I/O needs and the inputting of
@ real numbers. They are not designed to handle all I/O.
@ * BOXV is for demonstration only. It directly or indirectly
@ makes use of all the other sets.
@ * RUN makes interfaces cleaner by taking program objects off the
@ stack if the [ATTN] key is pressed. It will also return the
@ user to the menu used before the program was run.
@ * IPMO adds flexibility by allowing the user to choose a menu option
@ or the stack at an INPUT prompt. It makes use of PAUSE.
@ * CIA makes interfaces more robust by checking for bad input of real
@ numbers and telling the user what's wrong. It will also do
@ conversions with unit objects (including ones that have the
@ underscore missing.)
@ * PAUSE uses an alarm to halt program execution for any number of
@ seconds. It can also be used to update the stack display.
@ (NOTE: Subprogram EB in the RUN set is also used by IPMO and CIA)
@ All of the subprograms have been written as straightforwardly as
@ possible to allow for modifications. The only programming trick
@ that is used is to store some objects as strings. This technique
@ was used four times in IPMO to save about 210 bytes. Note, however,
@ that doing this makes the code less obvious and slower to a small
@ degree.
@*********************************************************************
@ BOXV: Box Volume Example
@ BV is just an example program for showing how IPMO and CIA can be
@ used. BOXV uses RUN to execute BV. BOXV or BV will ask the user
@ to input the volume of a box or it will CALC'ulate it from the
@ dimensions. A volume of 1.2_ft^3 is used to demonstrate the use of
@ default values. To really see why the user interface can be called
@ professional, try entering negative numbers or gibberish, entering
@ 3ft^3 instead of 3_ft^3 or pressing the ATTN key while running BOXV.
@ Executing ERUN demonstrates how RUN deals with an error caused by
@ something other than pressing the ATTN key. See the sections below
@ this one for more information about RUN, IPMO and CIA.
BOXV @ Compute Box Volume ( --> box_volume ) BYTES # 61780d 35.5
\<< 'BV' RUN \>>
BV @ Subprogram for BOXV ( --> box_volume ) BYTES # 57289d 419
\<<
DO
"Box Volume?" ":V:" "1.2_ft^3" 45 {"CALC"} IPMO
IF THEN
43 {1_ft 'x > 0'} \-> M C \<<
DO M TMENU "Box Width?" ":W:" INPUT C CIA UNTIL END
DO M TMENU "Box Depth?" ":D:" INPUT C CIA UNTIL END
DO M TMENU "Box Height?" ":H:" INPUT C CIA UNTIL END
* * 1 \>>
ELSE { 1_ft^3 'x > 0'} CIA END
UNTIL END 1_ft^3 * "V" \->TAG
\>>
ERUN @ Example of RUN catching an error ( --> ) BYTES # 31101d 40
@ Note that a list can be evaluated.
\<< { "" 2 * } RUN \>>
@*********************************************************************
@ RUN: Evaluate Object and Trap Errors
@ RUN is designed to evaluate programs and other objects. If the [ATTN]
@ key is pressed while using RUN, the stack will be reset to the input
@ stack. Unlike the LASTSTACK operation, it does not require the user
@ to press any additional keys or have any particular flag setting.
@ Using RUN will bring the back the menu and flag settings used before
@ the program started.
@ Note that there are some cases where pressing the [ATTN] key may not
@ be caught by RUN:
@ * If [ATTN] is pressed "immediately" after starting RUN
@ * If [ATTN] is pressed two are more times "rapidly"
@ * If the program being evaluated by RUN contains an IFERR command
@ RUN STACK INPUT
@ Level 1: Object to be evaluated by RUN
@ (other levels may contain input for the object)
@ RUN STACK OUTPUT
@ If [ATTN] was "not" pressed, the stack will contain the output of
@ the object evaluated by RUN.
@ If [ATTN] was pressed or the object evaluated with an error,
@ the stack will be reset to the input stack minus level 1.
RUN @ Evaluate Object BYTES # 57031d 276
\<<
DEPTH ROLLD DEPTH 1 - \->LIST RCLMENU RCLF \-> prg stk men flg
\<<
IFERR stk LIST\-> DROP prg EVAL THEN
IF ERRN #0d SAME NOT THEN
CLLCD "An error has occurred" 1 DISP "while evaluating..." 2 DISP
prg 3 DISP ERRN 5 DISP ERRM 6 DISP EB 3 FREEZE END
DEPTH DROPN stk LIST\-> DROP END
flg STOF men TMENU
\>> \>>
EB @ Error Beep ( --> ) BYTES # 32606d 33.5
\<< "1400 .1" STR\-> BEEP \>>
@*********************************************************************
@ IPMO: INPUT with MENU Options
@ IPMO may be used instead of (really in addition to) the built-in
@ INPUT command. It allows the user to choose a menu option rather
@ than inputting the requested data. It also allows the user to
@ access an empty stack to compute the input if necessary.
@ IPMO STACK INPUT
@ Level 5: INPUT command "stack prompt" (3 lines or less)
@ Level 4: INPUT command "command-line prompt" (list not allowed)
@ Level 3: Default value, any object, (should be "" if no default)
@ Level 2: Menu displayed during stack INPUT (real number or list)
@ Level 1: Menu displayed during menu INPUT (must be a list)
@ IPMO STACK OUTPUT
@ Level 2: INPUT command "result" if 0 in level 1
@ Level 1: Exit Condition, 0 for INPUT, 1 to 6 for menu key
@ When the user is asked for input by IPMO, one of five things happens
@ depending on which key is pressed first:
@ ( 1.) [ENTER] key will cause IPMO to end. The default value and
@ a 0 will be the stack output.
@ ( 2.) [0],[1],[2],...,[9],[.],backspace or [EXX] keys will cause
@ the 2nd level menu to be displayed and the real INPUT command will
@ be executed with the appropriate data appended to the command line
@ prompt. The default, if any, will vanish from the display. The
@ "result" from INPUT and the number 0 will be the stack output.
@ ( 3.) Any menu key that is not blank will cause IPMO to end.
@ A number from 1 to 6 corresponding to the menu key (going left to
@ right) will be the stack output.
@ ( 4.) [CONT] will cause the stack to be saved and IPMO to HALT.
@ An empty stack is then available for the user to compute the
@ required input. When [CONT] is pressed again, IPMO will make
@ the object in level 1 a string and leave it and 0 on the stack.
@ ( 5.) [ATTN] key will cause an error. An error trap should be
@ used outside of IPMO. RUN is recommended.
@ Pressing any other key will result in an error tone. The
@ only exceptions are shifted versions of most of the keys above.
@ Only [CONT] and [ATTN] are shift sensitive.
IPMO @ INPUT with MENU Options BYTES # 48856d 669.5
\<<
5 DUPN CLLCD TMENU DROP + 3 \->GROB SWAP 3 DISP
"(Press CONT for stack)" 1 DISP
LCD\-> "{#0d#46d}" STR\-> ROT REPL \->LCD
@sON EN M6 M5 M4 M3 M2 M1 [0][1][2][3][4][5][6][7][8][9][.][<][EXX]
@ -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13
"{91 51 16 15 14 13 12 11 92 82 83 84 72 73 74 62 63 64 93 55 53}"
STR\->
DO
DUP -1 WAIT IP POS 8 -
CASE DUP
1 \>= THEN C$ 41 {"0""1""2""3""4""5""6""7""8""9"".""""1E"} STR\->
SWAP GET 5 ROLLD DROP2 TMENU DROP + INPUT 0 1 END DUP
-5 \>= THEN NEG 1 + 3 PICK C$ 14 {""""""""""""} STR\-> + OVER GET
IF "" \=/ THEN 7 ROLLD 6 DROPN 1
ELSE EB NOT END END DUP
-6 == THEN 4 DROPN + SWAP DROP 0 1 END
-7 == THEN DROP2 TMENU 3 DROPN DEPTH \->LIST \-> \255 \<<
0 PAUSE "Place desired input on
stack level 1 and then
press CONT to continue
running program." 1 DISP 3 FREEZE HALT
IF DEPTH THEN \->STR DEPTH ROLLD DEPTH 1 - DROPN
ELSE "" END \255 LIST\-> 1 + ROLL \>> 0 1 END
EB 0 END
UNTIL END
\>>
@*********************************************************************
@ CIA: Check Input Acceptability
@ CIA will verify that the user has INPUT a valid real number based on
@ a check list. The real number may be tagged or have units but it
@ must be contained in a string. CIA will use ERR to display what
@ is wrong to the user if the INPUT value is not acceptable.
@ CIA STACK INPUT
@ Level 2: "result", INPUT value
@ Level 1: { unt rng }, check list (see below)
@ CIA STACK OUTPUT
@ Level 2: new_result, if 1 in Stack level 1 (real number)
@ Level 1: OK_flag, 1 if "value" OK, 0 otherwise
@ The check list must contain two values:
@ unt = the desired input units. unt=1 if units will be ignored.
@ If the unt is anything else, the INPUT value will be
@ CONVERT'ed to those units and then the units will be removed.
@ The new_result will be a real number without tags or units.
@ 'rng'= an expression which results in 1 if the INPUT value is
@ within range or 0 if not. The expression must refer to the
@ INPUT value as 'x' as in 'x\>=0' or '2<ABS(x) AND ABS(x)<3'.
@ If rng=1, any INPUT value will be within range.
@ Note that you may want to tell the user what units are required (if
@ any) and what range of values are allowable. This could be done as
@ part of the prompt messages for INPUT or IPMO.
@ Also note that during the INPUT command, PRG entry mode is used.
@ This will cause 3_ft^3 to be entered as 3ft^3 unless you explicitly
@ type in "_" character. CIA is smart enough, with the help of ISU,
@ to recognize and compensate for this in virtually every case. In
@ other words, 3ft^3 will be treated like 3_ft^3 so the user does not
@ have type the "_" character when using units.
CIA @ Check Input Acceptability BYTES # 57037d 590.5
\<<
DEPTH SWAP LIST\-> DROP \-> dep unt rng \<<
CASE
IFERR STR\-> THEN
ISU IFERR STR\-> THEN 1
ELSE 0 END ELSE 0 END THEN DROP " Invalid Syntax" ERR END
DEPTH dep - 1 +
IF DUP 1 == THEN
ROT DTAG 3 ROLLD
IF
3 PICK TYPE 0 ==
3 PICK TYPE DUP 6 ==
SWAP 7 == OR AND
THEN
DROP _ 0
END END DUP THEN 1 + DROPN "Only One Value Allowed"
ERR END DROP
DTAG DUP TYPE DUP 13 == XOR THEN DROP "Must be a Real Number" ERR END
unt 1 SAME NOT OVER TYPE AND
IF THEN IFERR unt CONVERT
THEN 1 ELSE UVAL 0 END
ELSE UVAL 0 END THEN DROP2 " Inconsistent Units" ERR END
rng { x } 3 PICK + \|^MATCH
DROP \->NUM NOT THEN DROP " Value Out of Range" ERR END
1 END
\>> \>>
ISU @ Insert Underscore Character BYTES # 39323d 196.5
@ ( "ValueUnits" --> "Value_Units" )
\<<
DUP SIZE 1
IF DUP2 \>= THEN FOR n
IF "0123456789" OVER n DUP SUB POS THEN
IF "^" OVER n 1 - DUP SUB \=/ THEN
DUP 1 n SUB "_" + SWAP n 1 + MAXR
\->NUM SUB + 0 'n' STO END END
-1 STEP ELSE DROP2 END
\>>
ERR @ Display Input Error ( "message" --> 0 ) BYTES # 10754d 87
\<< CLLCD "Sorry, not acceptable:" 3 DISP
5 DISP {"OK"} TMENU EB -1 WAIT DROP 0 \>>
@*********************************************************************
@ PAUSE: Timed Program HALT
@ PAUSE will set an alarm and HALT. The alarm will CONT the program
@ after a given number of seconds. One reason why this is useful is
@ that it allows the calculator time to update the stack display.
@ PAUSE uses ATCT and ADDT to do some date and time arithmetic. They
@ use HP 48 HMS and Date formats.
PAUSE @ Timed Program HALT ( seconds --> ) BYTES # 19068d 88
\<< .2 MAX 3600 / \->HMS MEM DROP ATCT
\<< DELALARM CONT \>> + STOALARM DROP HALT \>>
ATCT @ Add Time to Current Time BYTES # 30370d 38.5
@ ( Delta_Time --> {Date2 Time2} ) Computes Time2 and Date2 by adding
@ Delta_Time to the current Time and Date.
\<< DATE TIME 2 \->LIST SWAP ADDT \>>
ADDT @ Add Time to a Date and a Time BYTES # 50943d 77
@ ( {Date1 Time1} Delta_Time --> {Date2 Time2} )
@ Computes Time2 and Date2 by adding Delta_Time to Time1 and Date1.
\<< SWAP LIST\-> DROP ROT HMS+ DUP 24 / IP
ROT SWAP DATE+ SWAP 24 MOD 2 \->LIST \>>
@*********************************************************************
END