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ASCII codes for special keys
Hi! I need the codes for the keys "End" and "PageDown". They're not on the ASCII table. When I type "man ascii" they're not mentioned on the list.
I need to treat these keys and I don't know how to treat special keys.
Thanks.
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Answers
The reason they're not in an ASCII table, is that they're not ASCII keys. Imladris is right - it's a system dependant thing. On most machines a two-key code is generated, this is shown in fviellet's answer for a Unix terminal. On most PCs the BIOS will generate a 0 for what are known as the 'extended' ASCII keys, as a flag showing that there will be another byte, and then the values for the extended keys.
Well you add 256 to the keycode. It works somewhat like this:
The keyboard returns a 16 bit string, of which one byte is your ascii code. The zero is merely because this information is in the other byte.
So you read in two chars, if the first is zero check keycode of second, else first is desired key. I did this on dos.
Else you can read in the full int value and decide.
end = 256 + 79 = 335, and so on.
This is getting interesting as it goes... Thank you, DVB. I'll try it tonight and then feed back you all.
I'm a C programmer, but the reason why I'm so interested in these codes right now is that DOOM for Linux uses a file called
~/.doomrc
for it's configuration. I have to supply the keycodes in ASCII on this file to map the keyboard.
If this doesn't work now, I'll try to find a DOS/Windows machine to install DOOM and run the "SETUP.EXE" application, that is much more friendly and writes a configuration file, I believe it's 'default.cfg'. It's the equal to the '~/.doomrc' file.
try this program this works!!!
int readkey(int *is_function_key)
{
int c;
*is_function_key=0; //assume normal key is pressed
c=getch(); // no echo on the screen
if (c==0)
{
c=getch(); //the ascii code of the key
*is_function_key=1; //yes! this looks suspicious
}
return(c);
}
write this funtion in your main program and call it as follows
c=readkey(&is_pgdn);
compare c with the ascii values of the pgdn (they are already given by others!! so no need to repeat) and is_pgdn with `1'. you're on!!!
I won't be able to evaluate this solution now. I've changed my on-board SiS 5598 for a Trident 9680 and my DOOM stopped working. It's strange, as Quake continued to work. DOOM now has a crappy screen and when I leave it, the console is trashed, filled with error colorful characters. I can't even restore it with the 'reset' command. Fortunatelly I've mapped CTRL+ALT+DEL to 'shutdown -h now', so I can make a clean exit in the system.
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by: fveilletPosted on 1999-10-06 at 06:42:53ID: 2103278
If you're using a VT220 terminal emulator or the like, these keys are Control Sequences. The usually are a combinaison of the Escape keyes followed by several other keys.
You can easily find descriptions of these key sequences in VT220 documentation for programmers.
Also an easy way to find a sequence is with the "cat" command. Like this:
$ cat >seq
<Type the key>
<CTRL-D>
$ vi seq
Now you should see the complete key sequence. As I said, usually starting with Escape key, displayed as ^[
Hope this helps.