getch problem

[rajesh1978]

Hi
can any one plaase tell me the VC++ (or Dev C++) equivalent of the getch() function (Turbo C++ under DOS). I am converting an old DOS based project to VC++ and Dev C++ consols application. but i found that the function getch() is showing different behavior. In Turbo C++ (under DOS) when i press Alt + F it was resulting in to a sequence of two numbers i.e ZERO and another numeric value. but in VC++ and Dev C++ it is returning the ascii value of 'F'.

so in short i want a function in VC++/Dev C++, which can detect and return values for such key combinations like Alt+KEY, Ctrl+KEY.

For more information please look at the code

Can any one change this function “int getKey()” below so that it can identify Key combination like Alt+f, Ctrl+f etc.

int isPrintable(int ch)
{
// Returns true if ch is a printable character
if(ch>126 || ch<32)
return false;
else
return true;
}

int getKey()
{
/*

This function need change as in case of Dev C++, Alt+Key, Ctrl+Key are producing
the same ASCII values as thet of the Key itself. Example Alt + f = f =102.
*/
int ch;
ch=getch();
if(isPrintable(ch)) // Ordinary key
return ch;
else
{
if(ch==224 || ch==0) // Special key
ch=getch();
ch+=1000; // Adding 1000 for special keys so that they can be identified
return ch;
}
}

Target:
Windows, VC++/Dev C++





Thanks

[Dino]

I think you are going to have to use a different function to get the modifier keys, but I couldn't tell you which one without looking it up myself.

[cpjust]

Did you read the MSDN description of _getch()

None of these functions can be used to read CTRL+C. When reading a function key or an arrow key, each function must be called twice; the first call returns 0 or 0xE0, and the second call returns the actual key code.

[Salem]

Was your answer to avoid putting code tags in your post to turn OFF Javascript?

[rajesh1978]

Hi
strangely, i found that the _getch() function is not returning 0 or 0xE0 as stated in the MSDN reference, how ever it is [ getch() ] doing so in Turbo C++ under DOS. Kindly check the following code

#include <stdio.h>
#include <conio.h>
#include <ctype.h>

int getKey() 
{
	/*
		This function need change as in case of Dev C++, Alt+Key, Ctrl+Key are producing
        the same ASCII values as thet of the Key itself. Example Alt + f = f =102.
	*/
    int ch;
    ch=_getch();
    
	if(ch==0xE0)// Special key
	{
		ch=_getch();
    	ch+=1000; // Adding 1000 for special keys so that they can be identified
	}
	
	return ch;
}

int main(void)
{

	int ch = 0;

	while(true)
	{
		ch = getKey();
		printf("\n&#37;d", ch);
	}
	
	return 0;
}

[matsp]

When compiled with gcc on Windows XP, it works as I would expect. If I press "home" on the keypad, it gives 1079, uparrow gives 1072. Pressing arrow-keys on the numeric portion of the keyboard gives 0 and some other number (e.g 72 for uparrow).

However, Windows appear to handle ALT before the _getch() can see it. You would need to use some other method to identify that ALT is pressed. GetAsyncKeyState(VK_MENU) would give you the state of the ALT key itself.

--
Mats