Receive arrow key input

tay · #1 12-Jun-2004, 01:21

how to receive arrow key : up,down,left,right input

for e.g.

char input;
if ( input == up ) // mean up arrow key
cout<< " up arrow key ";

thx

RonBurk · #2 12-Jun-2004, 23:23

For what version of what operating system would you like to do this? Also, are you already using a framework/library (such as MFC) that has it's very own custom way of dealing with this layered on top of operating system primitives?

WaltP · #3 13-Jun-2004, 01:25

Quote:

Originally Posted by tay

how to receive arrow key : up,down,left,right input

for e.g.

char input;
if ( input == up ) // mean up arrow key
cout<< " up arrow key ";

thx

Using standard C/C++ you can't. Some compilers have added extensions to the standard to allow this, but it's very compiler dependant.

sho · #4 13-Jun-2004, 04:28

Quote:

Originally Posted by tay

how to receive arrow key : up,down,left,right input

for e.g.

char input;
if ( input == up ) // mean up arrow key
cout<< " up arrow key ";

thx

Well, I think that if you are working with a standard console application you could use the <conio.h> include, and use its getch() function to get the key pressed. Example:

char input;
input=getch();

Then you could compare its value with the ASCII value of the key you wanted in your if statement.

if ( input == ASCII value of up arrow ) // mean up arrow key
cout<< " up arrow key ";

You could also use this to check for any other key.
Hope this gives you an idea.

tay · #5 13-Jun-2004, 10:41

Quote:

Originally Posted by sho

Well, I think that if you are working with a standard console application you could use the <conio.h> include, and use its getch() function to get the key pressed. Example:

char input;
input=getch();

Then you could compare its value with the ASCII value of the key you wanted in your if statement.

if ( input == ASCII value of up arrow ) // mean up arrow key
cout<< " up arrow key ";

You could also use this to check for any other key.
Hope this gives you an idea.

u suggestion are good, but i try before
arrowkey is not a standard input (i guess so)
even use getch() also nothing happen

WaltP · #6 13-Jun-2004, 12:59

Quote:

Originally Posted by tay

u suggestion are good, but i try before
arrowkey is not a standard input (i guess so)
even use getch() also nothing happen

Oh, you are using a compiler that has the non-standard function getch()? If you had mentioned that I could have given you an example...

The function and arrow keys are 2-character keys. First char is 0, 2nd char is the key. The following shows how to access the keys and will also give you the key-commbinations:

CPP / C++ / C Code:

#include <stdio.h>
#include <conio.h>  /* needed for kbhit and getch */
#include <ctype.h>  /* needed for isprint         */


int  main()
{
    int  ch;
    
    ch = -1;
    while (ch != 0x1B)              /* watch for an ESC */
    {
        if (kbhit())                /* check for a keystroke */
        {
            ch = getch();           /* get the key */
            printf("%02X", ch);
            if (isprint(ch)) printf("/%c", ch);
            if (ch == 0)            /* if it's 0... */
            {
                ch = getch();       /* get the next key */
                printf("  %02X", ch);
               if (isprint(ch)) printf("/%c", ch);
            }
            printf("\n");
        }
    }
    return 0;
}

tay · #7 14-Jun-2004, 12:06

Quote:

Originally Posted by WaltP

CPP / C++ / C Code:

                  printf("%02X", ch);         // what is %02X means?

                  isprint(ch)                    // what is isprint(ch)?

sorry C i not really well,
can u explain more a bit to me

i try to convert to c++ but unfortunately the output is different

WaltP · #8 15-Jun-2004, 00:30

CPP / C++ / C Code:

printf("%02X", ch);

This prints ch as a hex value, 2 characters, 0 filled. I find this much easier than that cout gobbledygook

CPP / C++ / C Code:

isprint(ch)

Tests a character to see if it's printable (ASCII 0x20 to 0x7E)

Just compile the program and see what it does...

tay · #9 15-Jun-2004, 11:57

thx WaltP
1 more question

if we mix with c and c++
will it cause any problem?

aaroncohn · #10 15-Jun-2004, 12:54

You can mostly use C with C++ (namespaces tend to divide the two), but don't try using C++ if you're using a compiler that only works for C.

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