In a msg of <06 Nov 92>, Jack Hammond writes to All:
-> How does Turbo Pascal (I have 5.0) read such non-character keys
-> as the function keys, insert, home, pgup etc., and alt-keys?
Ok. Well in posing this question, you're actually asking for two different parts of code. The ALT/CTRL/LSHIFT/RSHIFT keys, etc. all generate SCAN codes and cannot be read via the ch:=readkey, etc. commands. To find the scan code of a key, the following code can be used:
uses CRT,DOS;
var oldvec : pointer; { save old int 9 vec here }
scode : byte;
procedure INT9HANDLER; interrupt;
begin
scode:=port[$60]; { get the scan code }
if scode<>0 then
writeln(scode); { if not 0 then print }
port[$20]:=$20; { tell PIC were done }
end;
begin
writeln('Press ESC to quit ...');
getintvec($09,oldvec); { hook in }
setintvec($09,@int9handler);
scode:=0;
repeat { go until esc pressed }
until scode=1;
setintvec($09,oldvec); { uninstall }
end.
As you can see, it's easily modifyable to process the keys. Just change the interrupt handler to check for a certain scan code . and process it accordingly. There is a FASTER method to do this too, without the use of interrupts. All ALT/CTRL/SHIFT/etc. have their status bitmapped at adress $0000:$0417. By declaring a byte absolute to this position, you can check the status of the keys using simple AND/OR routines. The bitmap is as follows:
bits meaning
7 6 5 4 3 2 1 0
---------------------------------------
. . . . . . . 1 Right Shift
. . . . . . 1 . Left Shift
. . . . . 1 . . Ctrl
. . . . 1 . . . Alt
. . . 1 . . . . Scroll Lock
. . 1 . . . . . Num Lock
. 1 . . . . . . Caps Lock
1 . . . . . . . Insert Lock
---------------------------------------
As for standard keys like F1, ENTER, etc, use the following:
uses CRT;
procedure PRINT_KEY;
var ch : char;
begin
ch:=readkey;
if ch=#0 then { Key is extended. (Function keys, INS, etc)
begin
write('Extended + #');
ch:=readkey; { Read second key in extended sequence }
writeln(ord(ch));
end
else
writeln(ord(ch);
end;
The above will print out the character codes for the keys desired. To process them, a simple case statement as follows is all that is needed:
begin
ch:=readkey;
case ch of
#0 : begin
ch:=readkey;
case ch of
#80 : writeln('UpArrow');
end;
end;
#27 : writeln('ESC');
end;
end;
Well, I hope that this answers all your questions. It may be a bit unclear, but if so, don't hesitate to holler.
