Smart questions
Smart answers
Smart people
INTELLIGENT WORK FORUMS
FOR COMPUTER PROFESSIONALS

Member Login




Remember Me
Forgot Password?
Join Us!

Come Join Us!

Are you a
Computer / IT professional?
Join Tek-Tips now!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

Join Tek-Tips
*Tek-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Donate Today!

Do you enjoy these
technical forums?
Donate Today! Click Here

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.
Jobs from Indeed

Link To This Forum!

Partner Button
Add Stickiness To Your Site By Linking To This Professionally Managed Technical Forum.
Just copy and paste the
code below into your site.

QBasic FAQ

I/O

How would one use multiple keys in a game?
Posted: 18 Sep 03

this is a question that is asked often, mostly if you're making a game.  now, i'm not claiming i'm an expert on this, but i learned a few things.  

One of the main ways to detect multikey input is to make an array like this: kbd(127) the kbd array will hold the status of every key on the keyboard. now, you must capture a key.  this is done like this:

keypress = inp(96)

this will tell us which keys are depressed.  now, when you press a key it will return a value between 1 and 127 to the variable keypress. if you let go of a key, it will return the value of the key you let go plus 127 (or something like that) so therefore to detect a keypress, you must determine if keypress is actually a keypress.

if keypress < 128 then

kbd(keypress) = 1

else
kbd(keypress - 128) = 0

endif

to get rid of the nasty little beeping problem with the pc speakers, insert this code somewhere.  

 DEF SEG = &H40
  POKE &H1A, PEEK(&H1A + 2)


One of the main problems about multiple key input is stickiness: keys will often "stick", meaning that the program continues reading the key as if it is depressed, which is no fun for the user.

There are many multikey programs made in qb, some with a few problems, while some are perfect.  some need the num-lock to be turned off, so try turning off your numlock if you want your multikey program to work properly.    

I am in no way an expert, just someone trying to help other people.  my explanations may suck, but i managed to find many multikey programs on the net.  study them!!!

a multikey routine from toshi himself. it tends to stick quite a bit though, but still worth looking through to learn from.

DECLARE SUB numlockoff ()
'=======================================================
'QBMKEY - Pure QB multiple keyboard press handler
'by Toshihiro Horie (270fps on Athlon 950)
'Public domain, use as you wish.
'=======================================================
DEFINT A-Z
DIM kbd(255), keystate(255)
FOR k = 0 TO 255: keystate(k) = -((k AND 128) = 0): NEXT k

'extra precalcs for demo
DIM wrapx(-1 TO 320), wrapy(-1 TO 200)
wrapx(-1) = 319: FOR k = 0 TO 319: wrapx(k) = k: NEXT: wrapx(320) = 0
wrapy(-1) = 199: FOR k = 0 TO 199: wrapy(k) = k: NEXT: wrapy(200) = 0

numlockoff
SCREEN 13
x = 160: y = 100
LOCATE 1, 1: PRINT "QBMKEY - use arrow keys"
frame& = 0: t1! = TIMER
DO
    'clear keyboard buffer every other frame
    IF frame& AND 1 THEN DEF SEG = &H40: POKE &H1C, PEEK(&H1A): DEF SEG
   
    'Fill multikey state table
    'Each key entry indexed by scancode is either a 1 for depressed
    'or a 0 for released.
    k = INP(&H60): kbd(k AND 127) = keystate(k)

    'Look up left and right arrow in key state table to
    'determine x and y velocity.
    xv = kbd(77) - kbd(75)
    yv = kbd(80) - kbd(72)
   
    'update circle position based on effective velocity
    x = wrapx(x + xv)
    y = wrapy(y + yv)
    'draw circle during vsync
    WAIT &H3DA, 8
    CIRCLE (xold, yold), 4, 0
    CIRCLE (x, y), 4, 13
    xold = x: yold = y
    frame& = frame& + 1
LOOP UNTIL kbd(1) 'escape key exits

'Display demo keyboard polling and graphics update speed
elapsed! = TIMER - t1!
IF elapsed! <> 0 THEN PRINT frame& / elapsed!; "fps"
END

DEFSNG A-Z
SUB numlockoff
'Set NumLock and other shift keys off
'-----------------------------------------------------------
REM This is absolutely necessary, since the demo code assumes
REM a depressed key will always return a 0 in the lower 7 bits.
DEF SEG = &H40: POKE &H17, 0: DEF SEG
END SUB





this one if made by josh stribling.  although it sticks sometimes, it still works well.

DECLARE SUB SETKEYS ()
DECLARE SUB CLEARBUF ()
DECLARE SUB GETKEYS ()

CONST TRUE = -1: FALSE = 0

Dim SHARED KB(128), lastk

Dim SHARED KBUP, KBDOWN, KBLEFT, KBRIGHT, KBESC, KBLSHIFT, KBRSHIFT, KBCTRL, KBSPACE, KBALT
SETKEYS

px = 160
py = 100
Do
  ox = px
  oy = py
  GETKEYS   'GET KEYBOARD INPUT

  if KB(KBUP) then
    py = py - 1
  end if

  if KB(KBDOWN) then
    py = py + 1
  end if

  if KB(KBLEFT) then
    px = px - 1
  end if

  if KB(KBRIGHT) then
    px = px + 1
  end if

  if (px <> ox) or (py <> oy) then
    'move the character
    'draw the screen...
  end if

  'all your other code here...

Loop Until KB(KBESC) 'END ON ESC
End

Sub CLEARBUF()
  DEF SEG = &H40
  POKE &H1A, PEEK(&H1A + 2)
End Sub

'This Is the Main Sub that does all the work
Sub GETKEYS()
  K = INP(96)
  If K Then                  'KEY CHANGED
    If K < 128 Then          'KEY PRESSED
      KB(K) = True           'SET THE KEY
      lastk = K              'SET THE LAST KEY PRESSED MARKER
    Else                     '....ELSE...LAST KEY RELEASED
      If K = 170 Then        'NOTE: (SC) 170 IS RELEASE LAST KEY PRESSED
        KB(lastk) = False    'CLEAR LAST KEY PRESSED
      Else                   '...ELSE...OTHER KEY RELEASED
        KB(K - 128) = False  'CLEAR RELEASED KEY
      End If
    End If
  End If
  CLEARBUF 'CLEAR REGULAR KEY BUFFER KEY BUFFER (NO BEEPS)
End Sub

Sub SETKEYS()
  'These are common keys...
  KBUP = 72     'Up Arrow
  KBDOWN = 80   'Down Arrow
  KBLEFT = 75   'Left Arrow
  KBRIGHT = 77  'right Arrow
  KBESC = 1     'Esc Key
  KBLSHIFT = 42 'Left Shift
  KBRSHIFT = 54 'Right Shift
  KBCTRL = 29   'Ctrl Key
  KBSPACE = 57  'Space Bar
  KBALT = 56    'Alt Key
End Sub


This is a very nice multikey routine by Eric Carr.   It's small and works very well! comes with a nice example.

'===========================================================================
' Subject: SIMULTANEOUS KEY DEMO             Date: 03-18-96 (13:12)       
' Author:  Eric Carr                         Code: QB, QBasic, PDS        
' Origin:  FidoNet QUIK_BAS Echo           Packet: KEYBOARD.ABC
'===========================================================================
'Ok..Here is the sample keyboard routine I promised..I haven't tested it on any
'other computer excpet mine, but it should work for anyone..  This program lets
'you move a box around by pressing the arrow keys..The acual routine in only 4
'lines as i have marked..This program requires a minimum of a 486sx 25mhz if
'not compiled to run fast enough for all the keys to be updated..I also
'reprogrammed the internal timer from 18.2 to 30, so I could time it to 30 fps.
'To see if a key is being currently pressed, the variable KS is used (IF
'KS(75)=1 THEN button is pressed). Instead of ASCII, this uses scan codes,
'which you can look at in the QB help..Hope you can understand it! :)

 DEFINT A-Z: DIM B(300): CLS

 N& = 39772                  'Reprogram the timer to 30hz
 LB& = N& AND &HFF           'instead of 18.2 (for 30 frames
 HB& = (N& / 256) AND &HFF   'per second.)
 OUT &H43, &H3C: OUT &H40, LB&: OUT &H40, HB&

 DIM KS(255), SC(255), DU(255)
 FOR E = 0 TO 127      ' Setup key data table KSC()
 SC(E) = E: DU(E) = 1
 NEXT
 FOR E = 128 TO 255
 SC(E) = E - 128: DU(E) = 0
 NEXT

 SCREEN 13: COLOR 4
 LOCATE 10, 3: PRINT "Keyboard input routine by Eric Carr"
 COLOR 7: PRINT : COLOR 2
 PRINT "  Use the arrow keys to move the box."
 PRINT "Note that you can press two or more keys"
 PRINT "    at once for diagnal movement!"
 PRINT : COLOR 8: PRINT "          Press [Esc] to quit"
 X = 150: Y = 100: BX = X: BY = Y
 DEF SEG = 0
 POKE (1132), 0
 GET (X, Y)-(X + 15, Y + 15), B
 DO  'main loop
T:
 I$ = INKEY$       ' So the keyb buffer don't get full     \routine/
 I = INP(&H60)     ' Get keyboard scan code from port 60h   \lines/
 OUT &H61, INP(&H61) OR &H82: OUT &H20, &H20       '         \!!!/
 KS(SC(I)) = DU(I) ' This says what keys are pressed          \!/
 
 IF PEEK(1132) < 1 THEN GOTO T  'If not enough time was passed goto T
 POKE (1132), 0  'reset timer again
 BX = X: BY = Y
 IF KS(75) = 1 THEN XC = XC - 2: IF XC < -15 THEN XC = -15
 IF KS(77) = 1 THEN XC = XC + 2: IF XC > 15 THEN XC = 15
 IF KS(72) = 1 THEN YC = YC - 2: IF YC < -15 THEN YC = -15
 IF KS(80) = 1 THEN YC = YC + 2: IF YC > 15 THEN YC = 15
 IF XC > 0 THEN XC = XC - 1 ELSE IF XC < 0 THEN XC = XC + 1
 IF YC > 0 THEN YC = YC - 1 ELSE IF YC < 0 THEN YC = YC + 1
 Y = Y + YC: X = X + XC
 IF X > 300 THEN X = 300 ELSE IF X < 0 THEN X = 0
 IF Y > 180 THEN Y = 180 ELSE IF Y < 0 THEN Y = 0
 IF X <> BX OR Y <> BY THEN
 WAIT 936, 8: PUT (BX, BY), B, PSET
 GET (X, Y)-(X + 15, Y + 15), B: LINE (X, Y)-(X + 15, Y + 15), 9, BF
 END IF
 LOOP UNTIL KS(1) = 1 'loop until [Esc] (scan code 1) is pressed

 N& = 65535                      'Program the timer back to
 LB& = N& AND &HFF               '18.2hz before exiting!
 HB& = (N& / 256) AND &HFF
 OUT &H43, &H3C: OUT &H40, LB&: OUT &H40, HB&

 OUT &H61, INP(&H61) OR &H82: OUT &H20, &H20
 CLEAR   'need to have this if reprograming the timer
 END      'I think this ends the program. I'm not quite sure.. :)


This one was made by Joe huber jr., but not really.  the keyboard routine was from eric carr's keyboard handler.  

'===========================================================================
' Subject: MULTIKEY FUNCTION UPDATE          Date: 05-13-97 (14:46)       
' Author:  Joe Huber, Jr.                    Code: QB, QBasic, PDS        
' Origin:  huberjjr@nicom.com              Packet: KEYBOARD.ABC
'===========================================================================
DECLARE SUB KEYTEST (LOWERLIMIT!, UPPERLIMIT!)
DECLARE FUNCTION MULTIKEY (KEYNUM)

'MUTIKEY FUNCTION - LETS YOU TRAP SEVERAL KEYS AT ONCE (BETTER THAN INKEY$!!)
'
'USAGE:
'  riable=MULTIKEY(KEYNUM)
'WHERE KEYNUM IS THE KEY YOU WANT TO TRAP
'  riable = 1 IF KEY IS DEPRESSED, 0 IF IT ISN'T
'
'CALL KEYTEST(lower,upper)
'Use this to find new keycodes
'(unrem below to test)

' CALL KEYTEST(1, 200)

'Gives all keynums between 1 & 200
'If the 0 by the number becomes a 1, then the key with that keycode is
'currently being depressed

'EMAIL ME AT: huberjjr@nicom.com
'
'HAVE FUN!!!

'



CLS

X = 10: Y = 10
XX = X: YY = Y

DO

RIGHT = MULTIKEY(75)    ' GET SOME KEYS' STATUSES
LEFT = MULTIKEY(77)
UP = MULTIKEY(72)
DOWN = MULTIKEY(80)
SPACE = MULTIKEY(57)
ESC = MULTIKEY(1)

IF ESC = 1 THEN END    'TEMINATE WHEN ESCAPE IS PRESSED

IF TIMELOOP = 100 THEN             'THIS MOVES YOU AROUND
 IF RIGHT = 1 THEN X = X - 1
 IF LEFT = 1 THEN X = X + 1        'THE TIMELOOP   RIABLE DELAYS
 IF UP = 1 THEN Y = Y - 1          'MOVEMENT WITHOUT SLOWING DOWN
 IF DOWN = 1 THEN Y = Y + 1        'INPUT (WITHOUT IT YOU WOULD GO
 TIMELOOP = 0                      'WAAAAYYY TOO FAST)
END IF

IF X >= 80 THEN X = 80        'KEEPS YOU FROM GOING OFF THE SCREEN AND
IF X <= 0 THEN X = 1          'MAKING AN ERROR
IF Y >= 23 THEN Y = 23
IF Y <= 0 THEN Y = 1


IF SPACE = 1 THEN                    'CHANGES YOUTR SHAPE WHEN
 LOCATE Y, X: PRINT CHR$(94)         'YOU HIT SPACE
ELSE
 LOCATE Y, X: PRINT CHR$(127)
END IF

IF XX <> X OR YY <> Y THEN           'UPDATES YOUR POSITION
 LOCATE YY, XX: PRINT " "
 LOCATE Y, X: PRINT CHR$(127)
END IF


XX = X: YY = Y                     'TELLS ME WHERE I WAS LAST

TIMELOOP = TIMELOOP + 1

LOOP                 'LOOP (DUH...) :)

'THANX TO Eric Carr FOR FIGURING OUT HOW TO TRAP SEVERAL KEYS AT ONCE
'EVERYTHING ELSE WRITTEN BY ME,              

SUB KEYTEST (LOWERLIMIT, UPPERLIMIT)


DO
X = 1
Y = 1

 FOR I = LOWERLIMIT TO UPPERLIMIT
  TEST = MULTIKEY(I)
  LOCATE Y, X
  PRINT TEST; I
 
  IF Y < 23 THEN
   Y = Y + 1
  ELSE
   Y = 1
   X = X + 7
  END IF
 NEXT I

LOOP WHILE MULTIKEY(1) = 0
END
END SUB

FUNCTION MULTIKEY (KEYNUM)

 STATIC FIRSTIME, KEYS(), SC(), DU()

 IF FIRSTIME = 0 THEN
  DIM KEYS(255), SC(255), DU(255)
  FOR E = 0 TO 127              '\
  SC(E) = E: DU(E) = 1          '|
  NEXT                                   '|-ERIC CARR'S CODE--------------------\
  FOR E = 128 TO 255            '|                                     |
  SC(E) = E - 128: DU(E) = 0    '|                                     |
  NEXT                          '/                                     |
  FIRSTIME = -1                 '                                      |
 END IF                         '                                      |
                                '                                      |
 I$ = INKEY$       ' So the keyb buffer don't get full     \routine/ \ |
 I = INP(&H60)     ' Get keyboard scan code from port 60h   \lines/  |-/
 OUT &H61, INP(&H61) OR &H82: OUT &H20, &H20       '         \!!!/   |
 KEYS(SC(I)) = DU(I) ' This says what keys are pressed        \!/    /

MULTIKEY = KEYS(KEYNUM)


END FUNCTION


Now this one is one of the best keyboard handlers made by my friend sjzero.  instead of checking a range, it checks the and operator instead.  it's capable of many things. check it out!   


'___
' |he Code Post
' `-' Original Submission
' ===============================================================
' CONTRIBUTOR: Sj Zero
' DESCRIPTION: Simple, yet effective multikey routines
' DATE POSTED: Sat Sep 1 09:39:43 2001
' ===============================================================

'Completely altered QB multikey Keyboard routines by SJ Zero


'Completely altered QB multikey Keyboard routines by SJ Zero
'Original routines by John Anderson(multikey.bas)
'Look for it on QB45.COM to see the differences.

'Here is the perfect pure QB keyboard handler. I fixed the flaws of
'John Andersons original design, and added a few tricks of my own,
'such as testing the AND instead of a range.
'The code may be uglier now, but it does a lot more than the original did,
'such as letting the numlock be active, and the Shifts be used.

'note: The keyspressed$ routine is basically useless, so I didn't change it.
'To use this code in a game, just use a like like:
'if Keyflag%(1) then print "Hey ma, a useless example!"

'Also notice the change I made to the inkey% meant to clear the keyboard
'buffer. Now it clears the whole buffer on every frame. This may not be the
'fastest solution, but it is the least likely to mess up on a computer with
'a cheap keyboard bios.

'One final thing, this must be checked rather often compared to other keyboard
'routines. If too much time passes between readings, the keys tend to stay
'active, which is not any fun for the user.

'Enjoy!

DECLARE FUNCTION KEYSPRESSED$ ()

DIM SHARED Keyflag%(0 TO 127)
DO
  
    li% = i%
    i% = INP(&H60)
    IF i% = 170 OR i% = 54 OR i% = 42 THEN FOR a = 0 TO 127: Keyflag%(a) = 0: NEXT a
    IF (i% AND 128) THEN Keyflag%(i% XOR 128) = 0
    IF (i% AND 128) = 0 THEN Keyflag%(i%) = -1
    WHILE INKEY$ <> "": WEND
    IF i% = 1 THEN END

  IF i% <> li% THEN
    LOCATE 1, 1: PRINT KEYSPRESSED$
  END IF
  IF ext% THEN EXIT DO
LOOP
END

FUNCTION KEYSPRESSED$
  'A string of all the keys curently being pressed
  kp$ = ""
  FOR k% = 0 TO 127
    IF Keyflag%(k%) THEN
      kpa$ = LTRIM$(RTRIM$(STR$(k%))): kl% = LEN(kpa$)
      kpa$ = "*" + kpa$
      kp$ = kp$ + kpa$
    END IF
  NEXT k%
  kp$ = kp$ + "*"
  lk% = LEN(kp$)
  kp$ = kp$ + (SPACE$((40 - lk%)))
  KEYSPRESSED$ = kp$
END FUNCTION



The alternative is to use an assembler handler, but who wants assembly? ;)  

I welcome any complaints, as it'd for sure help me learn.  at least there are lost of examples! ;D





Back to QBasic FAQ Index
Back to QBasic Forum

My Archive

Close Box

Join Tek-Tips® Today!

Join your peers on the Internet's largest technical computer professional community.
It's easy to join and it's free.

Here's Why Members Love Tek-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close