CD Actual 15/CDACTUAL15.iso/cdactual/program/pascal/PASLIBR.ZIP/CH3_1.DOC

Text File | 1991-03-15 | 11.7 KB | 475 lines

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..head03ABiosKbdClr
■ Description

  Clear the keyboard buffer.


■ Summary

  Procedure BiosKbdClr;


■ Remarks

  BiosKbdClr uses the BIOS to clear any characters in the keyboard
  buffer waiting to be read.


■ See Also

  DosKbdClr


■ Example

  Program Example;
  Uses FPKbd;
  Var
     Ch : Integer;
  Begin
     BiosKbdClr;
     Ch := GetKey;
  End.

  In this example the keyboard buffer is flushed before reading a
  keystroke from the keyboard.
..page
..head03ABiosKbdGetElmt
■ Description

  Returns an integer value for the key pressed on the keyboard.


■ Summary

  Function BiosKbdGetElmt : Integer;


■ Remarks

  BiosKbdGetElmt will return an integer in the range of 0-388.  Use
  Appendix C as a guide to find the keyboard element code this
  function returns for a particular key pressed on the keyboard.
  When using DOS function calls there is not any method available to
  distinguish the difference between some keystokes and key
  combinations.  An example of this is the Enter key and the Ctrl-M
  keys, both return a value of 145. Key combinations using the control
  key with an alpha character and all other ascii characters will be
  offset by 132.


■ See Also

  BiosKbdRead, DosKbdGetElmt, DosKbdRead


■ Example

  Program Example;
  Uses FPKbd;
  Begin
     Writeln( 'Value of keypressed = ', BiosKbdGetElmt:1 );
  End.

  If Control-Break were pressed then zero would be displayed.  If the
  'A' were pressed then 197 would be displayed: (197 - 132 = 65).
..page
..head03ABiosKbdHit
■ Description

  Reports if a keystroke is waiting to be read from the keyboard
  buffer.


■ Summary

  Function BiosKbdHit : Boolean;


■ Remarks

  Using the BIOS services BiosKbdHit checks the keyboard status to
  determine if a key is waiting to be read from the keyboard buffer.


■ See Also

  DosKbdHit


■ Example

  Program Example;
  Uses FPKbd;
  Begin
     While ( Not BiosKbdHit ) Do
        Writeln( 'Keyboard buffer empty...' );
  End.

  This program will display the keyboard buffer empty phrase on a new
  line until a key is pressed on the keyboard.
..page
..head03ABiosKbdRead
■ Description

  Read a character from the keyboard.


■ Summary

  Procedure BiosKbdRead( Ch : String );

  Ch          returns a string of length zero, one, or two bytes long
              defining the key or key combination pressed from the
              keyboard.


■ Remarks

  BiosKbdRead reads a single character from the keyboard buffer.
  BiosKbdRead will return a zero, one, or two character string.  A
  null string indicates that Ctrl- Break was pressed.  A one-character
  string indicates a normal ascii character was read from the
  keyboard.  A two-character string indicates a special extended
  keyboard code.  Refer to appendix B for a list of the extended
  keyboard codes.  The data type definition for BiosKbdRead is an
  untyped variable using a minimum of three bytes.


■ See Also

  BiosKbdGetElmt, DosKbdGetElmt, DosKbdRead
..page
■ Example

  Program Example;
  Uses FPKbd;
  Var
     Ch : String;
  Begin
     BiosKbdRead( Ch );
     Case Ord( Ch[0] ) Of 
              0 : Writeln( 'Ctrl char pressed' );
             27 : Writeln( 'Other key comb used' );
        32..127 : Writeln( 'ASCII pressed' );
     End;
  End.

  In this example any key or key combination that is read from the
  keyboard will be grouped into one of three categories.

  If Ch[1] is equal to the null byte and the length byte is equal to
  two, then one of the control characters (0-31) was pressed.  This
  includes the enter key, backspace, tab, and key combinations that
  use the control and an ACSII character A-Z.  If Ch[1] is equal to
  #27 then some other key combination was used, generally involving
  the alt key or control key with one of the function keys or cursor
  movement keys.  The string length will be two.  If Ch[1] is in the
  range #32..#127 then an ASCII character was pressed.  The length
  will also be one, where as in the other two possibilites the length
  will be two.
..page
..head03ABiosKbdStat
■ Description

  Get the keyboard status byte


■ Summary

  Function BiosKbdStat : Integer;


■ Remarks


  BiosKbdStat returns the keyboard status byte as follows:

               BITS
  ─────────────────────────────────
  | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
  ─────────────────────────────────

   Bit   Bit Value    Key Pressed
   ---   ---------    ──────────-
    0        1        Right Shift
    1        2        Left Shift
    2        4        Control
    3        8        Alternate

                       Key Mode
                      ───────────
    4       16        Scroll Lock
    5       32        Num Lock
    6       64        Caps Lock
    7      128        Insert

  A one in the bit position means the condition is true and a zero in
  the bit position means the condition is false.
..page
■ Example

  Program Example;
  Uses FPKbd;
  Var
     i    : Integer;
     Done : Boolean;
  Begin
     i    := 0;
     Done := False;

     While ( Not Done ) Do Begin
        i := BiosKbdStat;
        If ( BiosKbdHit ) Then Begin

           If ( i And 2 ) <> 0 Then
              Done := True;

           ClrWin( 1, 1, 80, 25, 7 );

          If ( i And 16 ) <> 0 Then Writeln( 'Scroll Lock ON ' );
          Else                      Writeln( 'Scroll Lock OFF' );

          If ( i And 32 ) <> 0 Then Writeln( 'Num Lock ON ' );
          Else                      Writeln( 'Num Lock OFF' );

          If ( i And 64 ) <> 0 Then Writeln( 'Caps Lock ON ' );
          Else                      Writeln( 'Caps Lock OFF' );

          If ( i And 128 ) <> 0 Then Writeln( 'Insert ON ' );
          Else                       Writeln( 'Insert OFF' );
        End;
     End;
  End.

  In this example everytime a key is pressed the screen is cleared and
  the status for the Scroll Lock, Insert, Caps Lock and Num Lock keys
  is displayed in the upper left corner.  This routine will not
  terminate until a key is pressed with the left shift key held down.
..page
..head03ADosKbdClr
■ Description

  Clear the keyboard buffer.


■ Summary

  Procedure DosKbdClr;


■ Remarks

  DosKbdClr uses DOS to clear any characters in the keyboard buffer
  waiting to be read.


■ See Also

  BiosKbdClr


■ Example

  Program Example;
  Uses FPKbd;
  Var
     Ch : Integer;
  Begin
     DosKbdClr;
     Ch := GetKey;
  End.

  In this example the keyboard buffer is flushed before reading a
  keystroke from the keyboard.
..page
..head03ADosKbdGetElmt
■ Description

  Returns an integer value for the key pressed on the keyboard.


■ Summary

  Function DosKbdGetElmt : Integer;


■ Remarks

  DosKbdGetElmt will return an integer in the range of 0-388.  Use
  Appendix C to find the keyboard element code this function returns
  for a particular key pressed on the keyboard.

  Key combinations using the control key with an alpha character and
  all other ascii characters will be offset by 132.


■ See Also

  BiosKbdGetElmt, BiosKbdRead, DosKbdRead


■ Example

  Program Example;
  Uses FPKbd;
  Begin
     Writeln( 'Value of keypressed = ', DosKbdGetElmt:1 );
  End.

  If Control-Break were pressed then zero would be displayed.  If the
  'A' were pressed then 197 would be displayed: (197 - 132 = 65).
..page
..head03ADosKbdHit
■ Description

  Reports if a keystroke is waiting to be read from the keyboard
  buffer.


■ Summary

  Function DosKbdHit : Boolean;


■ Remarks

  Using the DOS services DosKbdHit checks the keyboard status to
  determine if a key is waiting to be read from the keyboard buffer.


■ See Also

  BiosKbdHit


■ Example

  Program Example;
  Uses FPKbd;
  Begin
     While ( Not DosKbdHit ) Do
        Writeln( 'Keyboard buffer empty...' );
  End.

  This program will display the keyboard buffer empty phrase on a new
  line until a key is pressed on the keyboard.
..page
..head03ADosKbdRead
■ Description

  Read a character from the keyboard.


■ Summary

  Procedure DosKbdRead( CHAR PTR Ch );

  Ch          returns a string of length zero, one, or two bytes long
              defining the key or key combination pressed from the
              keyboard.


■ Remarks

  DosKbdRead reads a single character from the keyboard buffer.
  DosKbdRead will return a zero, one, or two character string.  A null
  string indicates that Ctrl- Break was pressed.  A one-character
  string indicates a normal ascii character was read from the
  keyboard.  A two-character string indicates a special extended
  keyboard code.  Refer to appendix B for a list of the extended
  keyboard codes.  The data type definition for DosKbdRead is an
  untyped variable using a minimum of three bytes.


■ See Also

  BiosKbdGetElmt, BiosKbdRead, DosKbdGetElmt
..page
■ Example

  Program Example;
  Uses FPKbd;
  Var
     Ch : String;
  Begin
     DosKbdRead;
     Case Ord( Ch[0] ) Of
              0 : Writeln( 'Ctrl char pressed' );
             27 : Writeln( 'Other key comb used' );
        32..127 : Writeln( 'ASCII pressed' );
     End.
  End.

  In this example any key or key combination that is read from the
  keyboard will be grouped into one of three categories.

  If Ch[1] is equal to the null byte and the length byte is equal to
  two, then one of the control characters (0-31) was pressed.  This
  includes the enter key, backspace, tab, and key combinations that
  use the control and an ACSII character A-Z.  If Ch[1] is equal to
  #27 then some other key combination was used, generally involving
  the alt key or control key with one of the function keys or cursor
  movement keys.  The string length will be two.  If Ch[1] is in the
  range #32..#127 then an ASCII character was pressed.  The length
  will also be one, where as in the other two possibilites the length
  will be two.
..page
..head03AGetKey
■ Description

  Returns a keystroke and map it into a keyboard element number for
  EditSt.


■ Summary

  Function GetKey : Integer;


■ Remarks

  This function may call other functions and procedures if it so
  desires. The only restriction is that it must return an integer
  value that is in the table found in Appendix C if the function
  EditSt is used.  If EditSt is not used the only restriction is that
  an integer must be returned.


■ Example

  Program Example;
  Uses FPVideo,FPKbd;

  Function GetKey : Integer;
  Var
     i : Integer;
  Begin
     While ( Not DosKbdHit ) Do Begin
        FillRowChar( 1, 25, 80, ' ' );

        i := BiosKbdStat;

        If ( i And  16 ) <> 0 Then ColorMsg(  1, 25, 7, 'Scroll');
        If ( i And  32 ) <> 0 Then ColorMsg(  8, 25, 7, 'Num'   );
        If ( i And  64 ) <> 0 Then ColorMsg( 12, 25, 7, 'Caps'  );
        If ( i And 128 ) <> 0 Then ColorMsg( 17, 25, 7, 'Insert');
     End.
     GetKey := BiosKbdGetElmt;
  End;

  Begin
     Writeln( 'Key element number = ', GetKey:1 );
  End.

  This example polls the keyboard, gets the keyboard status byte and
  displays the status for four keys while a key has not been pressed.
  Once a key has been pressed on the keyboard the BiosKbdGetElmt
  function is called to get the keyboard element number.
..page