CODEWITHSUNDEEP
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Rasmi Ranjan Nayak
Rasmi Ranjan Nayak

Reputation: 11968

Why getch() is throwing an error in C

I am running a C program in Code :: Blocks in windows XP. I am getting an error as 

"drawing operation is attempeted when there was no current window"

What might cause this and how can I solve it? My code is as follows:

#include <stdio.h>
#include <conio.h>
static int get_code(void);
// System dependent key codes
enum
{
    KEY_ESC     = 27,
    ARROW_UP    = 256 + 72,
    ARROW_DOWN  = 256 + 80,
    ARROW_LEFT  = 256 + 75,
    ARROW_RIGHT = 256 + 77
};
int main(void)
{
    int ch;
    puts("Press arrow keys, escape key + enter to exit:");
    while (( ch = get_code()) != KEY_ESC )
    {
        switch (ch)
        {
        case ARROW_UP:
            printf("UP\n");
            break;
        case ARROW_DOWN:
            printf("DOWN\n");
            break;
        case ARROW_LEFT:
            printf("LEFT\n");
            break;
        case ARROW_RIGHT:
            printf("RIGHT\n");
            break;
        }
    }
    getchar();   // wait
    return 0;
}
static int get_code(void)
{
    int ch = getch();    // Error happens here
    if (ch == 0 || ch == 224)
        ch = 256 + getch();
    return ch;
}

Upvotes: 1

Views: 6121

Answers (3)

Ahmed Jolani
Ahmed Jolani

Reputation: 3072

the α came from the getche() input, it prompts the user for input and when the user press a key then enter it echos that key on the standard output "screen" and since the arrows are non-printable keys that's what happened you can do something like like this:

switch (ch)
        {
        case ARROW_UP:
            printf("\bUP\n");
            break;
        case ARROW_DOWN:
            printf("\bDOWN\n");
            break;
        case ARROW_LEFT:
            printf("\bLEFT\n");
            break;
        case ARROW_RIGHT:
            printf("\bRIGHT\n");
            break;
        }

Upvotes: 1

Evert
Evert

Reputation: 593

Code::Blocks(MinGW) doesnt have conio.h header file. So you cant use the getch() function.

Upvotes: 0

Mohamed Jameel
Mohamed Jameel

Reputation: 602

actually conio.h is not standard header file which is not supported in Code :: Blocks http://en.wikipedia.org/wiki/C_standard_library

getch() definition found only in conio.h so it shows error try scanf to get user input.

Upvotes: 0

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