INKEY$ - QB64 Wiki

INKEY$

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The '''INKEY$''' Function returns user input as [[ASCII]] [[STRING]] character(s) from the keyboard buffer.
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The [[INKEY$]] function returns user input as [[ASCII]] [[STRING]] character(s) from the keyboard buffer.
{{PageSyntax}}
{{PageSyntax}}
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:: keypress$ = '''INKEY$'''
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: {{Parameter|keypress$}} = [[INKEY$]]
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''Usage:''
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{{PageDescription}}
* Returns [[ASCII]] character string values in upper or lower cases. See: [[UCASE$]] and [[LCASE$]]
* Returns [[ASCII]] character string values in upper or lower cases. See: [[UCASE$]] and [[LCASE$]]
* Returns "" if no key has been pressed since the last keyboard read.
* Returns "" if no key has been pressed since the last keyboard read.
* Some control keys cannot be read by INKEY$ or will return 2 byte [[ASCII]] codes.
* Some control keys cannot be read by INKEY$ or will return 2 byte [[ASCII]] codes.
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* INKEY$ can also clear a [[SLEEP]] keypress or the keyboard buffer in a loop.
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* INKEY$ can also be used to clear a [[SLEEP]] key press or the keyboard buffer in a loop.
* Assign the INKEY$ return to a string variable to save the key entry.
* Assign the INKEY$ return to a string variable to save the key entry.
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* [[LOCATE]] ,,1 displays the INKEY$ cursor. Use LOCATE ,,0 to turn it off.
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* <span style="font-family: Courier New, monospace, Courier; background: #dddddd">[[LOCATE]] , , 1</span> displays the INKEY$ cursor. Use <span style="font-family: Courier New, monospace, Courier; background: #dddddd">LOCATE , , 0</span> to turn it off.
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* Use [[_DEST]] [[_CONSOLE]] before INKEY$ statements to be used in a [[$CONSOLE|console]] window.
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* Use [[_DEST]] [[_CONSOLE]] before reading INKEY$ to receive input from a [[$CONSOLE|console]] window.
* Returns can be evaluated as certain [[ASCII]] characters or codes.
* Returns can be evaluated as certain [[ASCII]] characters or codes.
{{WhiteStart}}'                                '''ASCII Keyboard Codes'''
{{WhiteStart}}'                                '''ASCII Keyboard Codes'''
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==Two Byte Combinations==
==Two Byte Combinations==
* INKEY$ 2 byte combinations always begin with [[CHR$]](0). [[ASC]] will always read the first byte code as zero.  
* INKEY$ 2 byte combinations always begin with [[CHR$]](0). [[ASC]] will always read the first byte code as zero.  
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* QB64 can read the second byte code using: '''{{text|code2 <nowiki>=</nowiki> ASC(press$, 2)|green}}''' Qbasic can read it using: '''{{text|code2 <nowiki>=</nowiki> ASC(RIGHT$(press$, 1))|green}}'''
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* Read the second byte code using: '''{{text|code2 <nowiki>=</nowiki> ASC(press$, 2)|green}}'''
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:In '''QB64''', [[CVI]] can be used to get the [[_KEYDOWN]] 2-byte code value. Example: '''{{text|status <nowiki>=</nowiki> _KEYDOWN(CVI(CHR$(0) + "P"))|green}}'''
:In '''QB64''', [[CVI]] can be used to get the [[_KEYDOWN]] 2-byte code value. Example: '''{{text|status <nowiki>=</nowiki> _KEYDOWN(CVI(CHR$(0) + "P"))|green}}'''
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==Examples==
 
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{{PageExamples}}
''Example 1:'' Clearing the keyboard buffer after [[SLEEP]] delays for later [[INPUT]].
''Example 1:'' Clearing the keyboard buffer after [[SLEEP]] delays for later [[INPUT]].
{{CodeStart}}{{Cl|PRINT}} "Press any keyboard typing key to end SLEEP"
{{CodeStart}}{{Cl|PRINT}} "Press any keyboard typing key to end SLEEP"
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{{Cl|DO}}: K$ = {{Cl|INKEY$}}: {{Cl|PRINT}} K$: {{Cl|LOOP}} {{Cl|UNTIL}} K$ = "" '' ''
{{Cl|DO}}: K$ = {{Cl|INKEY$}}: {{Cl|PRINT}} K$: {{Cl|LOOP}} {{Cl|UNTIL}} K$ = "" '' ''
{{CodeEnd}}
{{CodeEnd}}
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:''Explanation:'' [[SLEEP]] key presses will be kept in the keyboard buffer and may be added into an [[INPUT]] later!
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:''Explanation:'' [[SLEEP]] key presses will be kept in the keyboard buffer and may be added into an [[INPUT]] later.
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:See also: [[_KEYCLEAR]]
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{{Cl|LOOP}} '' ''
{{Cl|LOOP}} '' ''
{{CodeEnd}} {{small|Adapted from code by Daniel}}
{{CodeEnd}} {{small|Adapted from code by Daniel}}
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: ''Note:'' The image can be placed off of the screen without error! The image moves 10 pixels to move faster. [[CLS]] eliminates any background.
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: ''Note:'' The image can be placed off of the screen without error. The image moves 10 pixels to move faster. [[CLS]] eliminates any background.
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''See also:''  
''See also:''  
* [[_KEYHIT]], [[_KEYDOWN]], [[_MAPUNICODE]]
* [[_KEYHIT]], [[_KEYDOWN]], [[_MAPUNICODE]]
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* [[_KEYCLEAR]]
* [[INPUT]], [[LINE INPUT]]
* [[INPUT]], [[LINE INPUT]]
* [[INPUT$]], [[INP]]  
* [[INPUT$]], [[INP]]  

Revision as of 04:25, 20 September 2017

The INKEY$ function returns user input as ASCII STRING character(s) from the keyboard buffer.


Contents

Syntax

keypress$ = INKEY$


Description

  • Returns ASCII character string values in upper or lower cases. See: UCASE$ and LCASE$
  • Returns "" if no key has been pressed since the last keyboard read.
  • Some control keys cannot be read by INKEY$ or will return 2 byte ASCII codes.
  • INKEY$ can also be used to clear a SLEEP key press or the keyboard buffer in a loop.
  • Assign the INKEY$ return to a string variable to save the key entry.
  • LOCATE , , 1 displays the INKEY$ cursor. Use LOCATE , , 0 to turn it off.
  • Use _DEST _CONSOLE before reading INKEY$ to receive input from a console window.
  • Returns can be evaluated as certain ASCII characters or codes.

' ASCII Keyboard Codes ' ' Esc F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 Sys ScL Pause ' 27 +59 +60 +61 +62 +63 +64 +65 +66 +67 +68 +133 +134 - - - ' `~ 1! 2@ 3# 4$ 5% 6^ 7& 8* 9( 0) -_ =+ BkSp Ins Hme PUp NumL / * - ' 126 33 64 35 36 37 94 38 42 40 41 95 43 8 +82 +71 +73 - 47 42 45 ' 96 49 50 51 52 53 54 55 56 57 48 45 61 ' Tab Q W E R T Y U I O P [{ ]} \| Del End PDn 7Hme 8/▲ 9PU + ' 9 81 87 69 82 84 89 85 73 79 80 123 125 124 +83 +79 +81 +71 +72 +73 43 ' 113 119 101 114 116 121 117 105 111 112 91 93 92 55 56 57 ' CapL A S D F G H J K L  ;: '" Enter 4/◄- 5 6/-► ' - 65 83 68 70 71 72 74 75 76 58 34 13 +75 +76 +77 E ' 97 115 100 102 103 104 106 107 108 59 39 52 53 54 n ' Shift Z X C V B N M ,< .> /? Shift ▲ 1End 2/▼ 3PD t ' * 90 88 67 86 66 78 77 60 62 63 * +72 +79 +80 +81 e ' 122 120 99 118 98 110 109 44 46 47 49 50 51 r ' Ctrl Win Alt Spacebar Alt Win Menu Ctrl ◄- ▼ -► 0Ins .Del ' * - * 32 * - - * +75 +80 +77 +82 +83 13 ' 48 46 ' ' Italics = LCase/NumLock On * = 2 byte combo only, + = 2 Byte: CHR$(0) + CHR$(code) '

Two Byte Combinations

  • INKEY$ 2 byte combinations always begin with CHR$(0). ASC will always read the first byte code as zero.
  • Read the second byte code using: code2 = ASC(press$, 2)


Two Byte Ctrl, Alt and Shift + Function key combinations

Two Byte Characters    Key                 CHR$(0) + "?" CHR$(0) + CHR$(16-50) [Alt] + letter CHR$(0) + CHR$(59) [F1] ";" CHR$(0) + CHR$(60) [F2] "<" CHR$(0) + CHR$(61) [F3] "=" CHR$(0) + CHR$(62) [F4] ">" CHR$(0) + CHR$(63) [F5] "?" CHR$(0) + CHR$(64) [F6] "@" CHR$(0) + CHR$(65) [F7] "A" CHR$(0) + CHR$(66) [F8] "B" CHR$(0) + CHR$(67) [F9] "C" CHR$(0) + CHR$(68) [F10] "D" CHR$(0) + CHR$(71) [Home] "G" CHR$(0) + CHR$(72) [↑] Arrow "H" CHR$(0) + CHR$(73) [Page Up] "I" CHR$(0) + CHR$(75) [←] Arrow "K" CHR$(0) + CHR$(76) [5 NumberPad] "L" (NumLock off in QB64) CHR$(0) + CHR$(77) [→] Arrow "M" CHR$(0) + CHR$(79) [End] "O" CHR$(0) + CHR$(80) [↓] Arrow "P" CHR$(0) + CHR$(81) [Page Down] "Q" CHR$(0) + CHR$(82) [Insert] "R" CHR$(0) + CHR$(83) [Delete] "S" CHR$(0) + CHR$(84-93) [Shift] + F1-10 CHR$(0) + CHR$(94-103) [Ctrl] + F1-10 CHR$(0) + CHR$(104-113) [Alt] + F1-10 CHR$(0) + CHR$(114-119) [Ctrl] + keypad CHR$(0) + CHR$(120-129) [Alt] + number CHR$(0) + CHR$(130 or 131) [Alt] + _/- or +/= "é" or "â" CHR$(0) + CHR$(133) [F11] "à" CHR$(0) + CHR$(134) [F12] "å" CHR$(0) + CHR$(135) [Shift] + [F11] "ç" CHR$(0) + CHR$(136) [Shift] + [F12] "ê" CHR$(0) + CHR$(137) [Ctrl] + [F11] "ë" CHR$(0) + CHR$(138) [Ctrl] + [F12] "è" CHR$(0) + CHR$(139) [Alt] + [F11] "ï" CHR$(0) + CHR$(140) [Alt] + [F12] "î"

In QB64, CVI can be used to get the _KEYDOWN 2-byte code value. Example: status = _KEYDOWN(CVI(CHR$(0) + "P"))


Examples

Example 1: Clearing the keyboard buffer after SLEEP delays for later INPUT.

PRINT "Press any keyboard typing key to end SLEEP" SLEEP DO: K$ = INKEY$: PRINT K$: LOOP UNTIL K$ = ""

Explanation: SLEEP key presses will be kept in the keyboard buffer and may be added into an INPUT later.
See also: _KEYCLEAR


Example 2: Entering a Ctrl + letter keypress combination will print ASCII Control characters 1 to 26. .

DO K$ = INKEY$ IF K$ <> "" THEN PRINT K$; " "; LOOP UNTIL K$ = CHR$(27) 'Esc key exit

Note: The above code will print Esc arrow, Backspace symbol, and 2 byte characters led by CHR$(0) in addition to normal keys.


Example 3: Use UCASE$(INKEY$) in a keyboard read loop looking for uppercase "Y" or "N" user inputs to avoid multiple IF statements.

DO PRINT "Do you want to continue? (Y/N): "; 'semicolon saves position for user entry DO: K$ = UCASE$(INKEY$) 'change any user key press to uppercase LOOP UNTIL K$ = "Y" OR K$ = "N" PRINT K$ 'print valid user entry IF K$ = "N" THEN END LOOP


Example 4: Getting just number values entered by a user in an INKEY$ input loop.

LOCATE 10, 10: PRINT "Enter a number value: "; DO: SLEEP K$ = INKEY$ IF K$ >= CHR$(48) AND K$ <= CHR$(57) THEN entry$ = entry$ + K$ ' numbers only L = LEN(entry$) ' check entry length for possible backspace IF K$ = CHR$(46) AND flag = 0 THEN entry$ = entry$ + K$: flag = 1: mark = L ' decimal point IF K$ = CHR$(8) AND L > 0 THEN ' backspace pressed and entry has a length entry$ = MID$(entry$, 1, L - 1) ' remove one character from entry$ IF LEN(entry$) < mark THEN flag = 0 ' allow decimal point entry if other was removed. LOCATE CSRLIN, POS(0) - 1: PRINT SPACE$(1); ' remove end character from screen END IF LOCATE 10, 32: PRINT entry$; ' display entry to user (semicolon required for correct POS) LOOP UNTIL K$ = CHR$(13) AND L > 0 'assures something is entered

Explanation: SLEEP waits for a keypress. It also allows background programs to share the processor and it leaves the keypress in the buffer for INKEY$. Keyboard string number characters range from ASCII codes 48 to 57. Any other entry is ignored by the IF statement. A decimal point (code 46) entry is allowed once in the input. The flag value stops further decimal point additions. Backspacing (code 8) is also allowed if the entry has at least one character. The cursor column returned by POS(0) reverts too after the end of the entry when printed each loop. The loop exits when [Enter] (code 13) is pressed and the entry has a length.


Example 5: Using arrow keys to move a text character. A change from a previous position tells program when to PRINT:

movey = 1: movex = 1 'text coordinates can never be 0 at$ = "@" 'text sprite could be almost any ASCII character LOCATE movey, movex: PRINT at$; DO px = movex: py = movey 'previous positions B$ = INKEY$ IF B$ = CHR$(0) + CHR$(72) AND movey > 1 THEN movey = movey - 1 'rows 1 to 23 only IF B$ = CHR$(0) + CHR$(80) AND movey < 23 THEN movey = movey + 1 IF B$ = CHR$(0) + CHR$(75) AND movex > 1 THEN movex = movex - 1 'columns 1 to 80 only IF B$ = CHR$(0) + CHR$(77) AND movex < 80 THEN movex = movex + 1 IF px <> movex OR py <> movey THEN 'only changes when needed LOCATE py, px: PRINT SPACE$(1); 'erase old sprite LOCATE movey, movex: PRINT at$; 'show new position END IF LOOP UNTIL B$ = CHR$(27) 'ESCape key exit END


Example 6: Using INKEY$ with the arrow or WASD keys to move the QB64 bee image sprite with _PUTIMAGE:

DIM image AS LONG DIM x AS INTEGER DIM y AS INTEGER DIM Keypress AS STRING SCREEN _NEWIMAGE(800, 600, 32) x = 0 y = 0 image = _LOADIMAGE("QB64bee.png") 'Here I actually used the QB64 icon DO _PUTIMAGE (x, y), image DO Keypress = UCASE$(INKEY$) ' ***** The following line detects the arrow keys ***** IF LEN(Keypress) > 1 THEN Keypress = RIGHT$(Keypress, 1) LOOP UNTIL Keypress > "" CLS ' blank screen after valid key press to avoid smearing image on page SELECT CASE Keypress CASE "W", "H": y = y - 10 'Up CASE "A", "K": x = x - 10 'Left CASE "S", "P": y = y + 10 'Down CASE "D", "M": x = x + 10 'Right CASE "Q", CHR$(27): END 'Q or Esc Ends prog. END SELECT _PUTIMAGE (x, y), image LOOP

Adapted from code by Daniel
Note: The image can be placed off of the screen without error. The image moves 10 pixels to move faster. CLS eliminates any background.


Example 7: Creating upper ASCII characters in a QB program using Alt + three number keys:

DO A$ = "": WHILE A$ = "": A$ = INKEY$: WEND IF LEN(A$) = 2 THEN '2 byte INKEY$ return B$ = RIGHT$(A$, 1) 'read second byte b% = ASC(B$) 'read second byte code IF b% > 119 AND b% < 130 THEN ' Alt + number codes only C% = b% - 119 ' convert to actual number IF C% > 9 THEN C% = 0 num$ = num$ + LTRIM$(STR$(C%)) END IF END IF LOOP UNTIL LEN(num$) = 3 ' 3 digit codes only PRINT num$ PRINT CHR$(VAL(num$)

Code by Ted Weissgerber

155 ¢

Explanation: Hold down Alt key and press 3 keyboard code number keys. Number pad keys may not work. Note that INKEY$ cannot read Alt, Ctrl or Shift key presses without a key combination and the return is CHR$(0) + CHR$(code).



See also:



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