ASCII - mkilgore/QB64pe GitHub Wiki

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ASCII and Extended Codes

MS-DOS code page 437:
ASCII Keyboard Character Codes 32 to 127
Code Character [key] Code Character Code Character Code Character
0 (NUL) 32 [Spacebar] 64 @ 96 `
1 ? (SOH) 33 ! 65 A 97 a
2 ? (STX) 34
* DEL was used to erase paper tape data by punching out all of the 7 holes.
** Control characters 8 to 13 and 28 to 31 can move text formatting when printed and do not display
*** NBSP is a Non-breaking Space used to indent text. Some browsers may handle this character differently
More information about ASCII Control Characters Unicode Character Table

Control Characters

  • INKEY$ will return Control + letter key press combinations as the equivalent control characters or bold function keys listed below:
   '''<span style="color:red;">Red symbols will format text and not [[PRINT]] the symbol.</span> [[_PRINTSTRING]] can print in QB64'''
  • Control characters 1 to 26 can be used to simulate Ctrl + letter key shortcuts in Windows programs using _SCREENPRINT.
  • _CONTROLCHR OFF can also be used in QB64 to allow control characters to be printed without formatting the text.
ASCII in Text and Printing
  • Characters 0(NULL) and 255(NBSP) can also be used to print spaces(32). Useful for making file names harder to delete too.
  • Character 7 will create a BEEP sound when printed in QB64 or an error sound in QBasic using a SCREEN 0 window.
  • Character 8 is returned when the Backspace key is pressed.
  • Characters 9 thru 13 and 28 thru 31 can affect screen or file text placements and do not display the character when printed:
  • Character 9 will Tab space the cursor 8 column spaces when printed.
  • Character 10 moves the cursor or "line feeds" the printer head down one row.
  • Character 11 vertical tabs the cursor back to top left position of page or screen. Acts like CLS.
  • Character 12 acts like CLS when printed. "Form feeds" the page out of printers.
  • Character 13 is the cursor or typing "carriage return" to the start of the line on left side. Returned when Enter key pressed.
  • Character 28 designates a File Separator. Moves the print cursor one space right. Combination Ctrl + \
  • Character 29 designates a Group Separator. Moves the print cursor one space left. Combination Ctrl + ]
  • Character 30 designates a Record Separator. Moves the print cursor one row up. Combination Ctrl + ^
  • Character 31 designates a Unit Separator. Moves the print cursor one row down. Combination Ctrl + _
  • QB64 can display all of the control characters without formatting the text using _PRINTSTRING.
  • Characters 13 and 10 can be combined to create the CrLf carriage return used in files or printing. crlf$ = CHR$(13) + CHR$(10).
  • Character 16, the data link escape(DLE) character, can designate that a control character is being sent from a COM port.
Example: (DLE) (DLE) or (DLE) (DLE)
  • Character 17, Device Control 1, is used with COM ports to mark the start of a transmission as "XON". The character is read.
  • Character 19, Device Control 3, is used with COM ports to mark the end of a transmission as "XOFF". The character is NOT read.
  • Character 26 can be used to designate the end of a file. See EOF.
  • Character 27 ? is returned when the Escape key is pressed.
Control character PRINT actions can be controlled using _CONTROLCHR OFF or ON in QB64. 
END '' ''
ASCII Character Usage
  • Characters are one byte and take up one space(byte) in a STRING value or variable.
  • Extended(non-keyboard) characters can be entered by holding down Alt key and entering the code number on the Number pad.
  • PRINTs text characters and symbols or formats the screen, printer or file.
  • BINARY files often store values below 256 in the one byte character. To read the value get the code with ASC.
  • Numerical values placed into a BINARY or RANDOM file using a GET or PUT variable, they will be stored in _MK$ format.
  • Characters 176 to 223 can be used to create screen borders or boundaries in an ASCII game. See: SCREEN (function)
  • Character 253(small 2) can be found as the first character byte of a BSAVEd image file opened in BINARY mode.
  • Character 255 can be used as the NBSP(non-breaking space) character on web pages to fill in extra spaces.
  • Can be used to crudely encrypt a file so others cannot read it by shifting the code values. See CHR$ example 2.

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ASC Codes

ASC cannot read empty INKEY$ = "" loop reads! Check for them before reading ASC key press 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: CHR$(0) + CHR$(code)'''
'<center><span style="font-family: Courier New, Courier, monospace; font-size: 0.80em; line-height: 50%;">NOTE: The above commented table can be copied and pasted directly into the QB64 IDE</span></center>
Use ASC(RIGHT$(key$, 1)) or ASC(key$, 2) in QB64 to read a two byte code when ASC(key$) = 0 * See the Two Byte Ctrl, Alt and Shift + Function key combinations below 
'             Demo displays all ASCII codes and 2 byte code combinations
DO...LOOP: K$ = INKEY$
  IF...THEN K$ <> "" THEN      'ASC will return an error if an empty string is read!
    IF...THEN ASC(K$) > 0 THEN
      PRINT "CHR$(" + LTRIM$(STR$(ASC(K$))) + ")"  'display normal keypress codes
    ELSE PRINT "CHR$(0) + CHR$(" + LTRIM$(STR$(ASC(K$, 2))) + ")"  'display 2 byte codes
    END IF
  END IF
LOOP UNTIL K$ = CHR$(27) 'escape key press exits '' ''
Note: In QB64 ASC(K$, 2) can read the second byte of the 2 byte code when ASC(K$) reads the first byte as 0.

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Two Byte Codes

Two Byte ASCII Keyboard Return Values
  • INKEY$ returns both bytes when two byte keys or key combinations are pressed. The second byte = RIGHT$(keypress$, 1)
  • If the character returned is a two byte code, ASC will return 0. Warning: ASC cannot read empty INKEY$ string values!
  • In QB64 only, ASC(keypress$, 2) can return the second byte code. Don't read empty string values!
  • String values returned can be compared in an IF or SELECT CASE routine by using the actual string definitions such as:
IF INKEY$ = CHR$(0) + CHR$(80) THEN row = row + 1 or IF INKEY$ = CHR$(0) + "P" THEN row = row + 1
                    CHR$(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$(72)         [?] Up Arrow         "H"
                    CHR$(0) + CHR$(73)         [Page Up]            "I"
                    CHR$(0) + CHR$(75)         [?] Left Arrow       "K"
                    CHR$(0) + CHR$(76)         [5 NumberPad]        "L" (NumLock off in QB64)
                    CHR$(0) + CHR$(77)         [?] Right Arrow      "M"
                    CHR$(0) + CHR$(79)         [End]                "O"
                    CHR$(0) + CHR$(80)         [?] Down Arrow       "P"
                    CHR$(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"))
See Scancodes for other keyboard function keys.

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Code Examples

Example 1: Using arrow keys to move a text character. A change from a previous position tells program when to PRINT: 

    IF...THEN px <> movex OR (boolean) 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 2: Routine displays all keypress codes including Ctrl, Alt and Shift combinations. Ctrl + letter = control codes 1 to 26. 

 '' ''
 SCREEN 13
 tmp$ = "   CHR$(###),\\,\          \       "
 tmp2$ = "  CHR$(0) + CHR$(###) \           \"
 COLOR 14: LOCATE 3, 3: PRINT "The code can tell what key is pressed"
 COLOR 12: LOCATE 5, 14: PRINT CHR$(3); SPACE$(3);
 COLOR 13: PRINT CHR$(5); SPACE$(3);
 COLOR 12: PRINT CHR$(4); SPACE$(3);
 COLOR 13: PRINT CHR$(6)
 COLOR 10: LOCATE 7, 4: PRINT " Hit a key to find the ASCII Code"
 COLOR 5: LOCATE 13, 1: PRINT " Codes below 33 are called control keys"
 LOCATE 14, 1: PRINT " CHR$(0) + are 2 byte Extended key codes"
 COLOR 13: LOCATE 16, 1: PRINT " Extended: Press Alt + numberpad: Enter"
 LOCATE 18, 1: PRINT "  Try some Ctrl, Alt, or Shift Combo's"
 COLOR 5: LOCATE 20, 1: PRINT " INKEY$ is used to detect the key entry"
 COLOR 2: LOCATE 22, 15: PRINT CHR$(1); "       "; CHR$(2)
 COLOR 4: LOCATE 24, 10: PRINT "To Quit hit the TAB key";

 COLOR 9
 DO
     DO: SLEEP: A$ = INKEY$: LOOP UNTIL A$ <> ""  'legal ASC read keys
     IF ASC(A$) > 0 THEN  ' normal key codes
         code% = ASC(A$)
         SELECT CASE code%
           CASE 7: Key$ = "Beep"
           CASE 8: Key$ = "Backspace"
           CASE 9: Key$ = "Tab Key"
           CASE 10: Key$ = "Line Feed"
           CASE 12: Key$ = "Form Feed"
           CASE 13: Key$ = "Enter"
           CASE 27: Key$ = "Escape"
           CASE 32: Key$ = "Space Bar"
           CASE 48 TO 57: Key$ = "Number"
           CASE 65 TO 90: Key$ = "Uppercase"
           CASE 97 TO 122: Key$ = "Lowercase"
           CASE ELSE: Key$ = ""
         END SELECT
         SELECT CASE code%  'check for unprintable control combo characters
           CASE 10 TO 13: Kcode% = 32
           CASE ELSE: Kcode% = code%
         END SELECT
         COLOR 9: LOCATE 10, 5: PRINT USING tmp$; code%; CHR$(Kcode%); Key$;
     END IF
     IF ASC(A$) = 0 THEN  'two byte key codes
         code% = ASC(RIGHT$(A$, 1)) 'QBasic code
         'code% = ASC(A$, 2)        'QB64 code alternative
         SELECT CASE code%
            CASE 16 TO 50: Key$ = "Alt+ letter"
            CASE 72: Key$ = CHR$(24) + " Arrow"
            CASE 75: Key$ = CHR$(27) + " Arrow"
            CASE 77: Key$ = CHR$(26) + " Arrow"
            CASE 80: Key$ = CHR$(25) + " Arrow"
            CASE 83: Key$ = "Delete"
            CASE 59: Key$ = "F1"
            CASE 60: Key$ = "F2"
            CASE 61: Key$ = "F3"
            CASE 62: Key$ = "F4"
            CASE 63: Key$ = "F5"
            CASE 64: Key$ = "F6"
            CASE 65: Key$ = "F7"
            CASE 66: Key$ = "F8"
            CASE 67: Key$ = "F9"
            CASE 68: Key$ = "F10"
            CASE 71: Key$ = "Home"
            CASE 73: Key$ = "Page " + CHR$(24)
            CASE 79: Key$ = "End"
            CASE 81: Key$ = "Page " + CHR$(25)
            CASE 82: Key$ = "Insert"
            CASE 83: Key$ = "Delete"
            CASE 84 TO 93: Key$ = "Shift+ F"
            CASE 94 TO 103: Key$ = "Ctrl+ F"
            CASE 104 TO 113: Key$ = "Alt+ F"
            CASE 114 TO 119: Key$ = "Ctrl + pad"
            CASE 120 TO 129: Key$ = "Alt+ number"
            CASE 132: Key$ = "Ctrl + pad"
            CASE 133: Key$ = "F11"
            CASE 134: Key$ = "F12"
            CASE 135: Key$ = "Shift+ F11"
            CASE 136: Key$ = "Shift+ F12"
            CASE 137: Key$ = "Ctrl+ F11"
            CASE 138: Key$ = "Ctrl+ F12"
            CASE 139: Key$ = "Alt+ F11"
            CASE 140: Key$ = "Alt+ F12"
            CASE ELSE: Key$ = ""
         END SELECT
         LOCATE 10, 5: PRINT USING tmp2$; code%; Key$
     END IF
 LOOP UNTIL A$ = CHR$(9)
 SOUND 400, 4
 SLEEP 3
 SYSTEM '' ''
Code by Ted Weissgerber Explanation: The routine checks for a keypress and SLEEP guarantees that ASC will never read an empty string from INKEY$. When the keypress is determined to be two bytes (ASC(A$) = 0) the second SELECT CASE routine is used. You can even display non-keyboard extended characters. Just press Alt + numberpad code, release and press enter.
Note: Ctrl + letter keys will list the contol keys as normal codes. EX: Ctrl + G will BEEP (CHR$(7)).

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References

Printable ASCII Table: _PRINTIMAGE (see Example 2 on page)

See also

Navigation:
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