打印按下的键 C++

Question

I want to capture and print pressed key. Problem is that my program show "a" as "A" and "1" as "a". And i dont know how to fix. Will be thankfull for any help. Cant use something like scanf or getc because it should be keylogger(consolefree) for my school project.

My source code:

#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <Windows.h>

using namespace std;

int main(){
char c;

    while(true)
    {
        for (int i = 8; i <= 255; i++)
        {
            if (GetAsyncKeyState(i) == -32767) // I DONT UNDERSTAND THIS LINE
            {
                c = char(i);
                printf("%c", c);
            }
        }
    }

    return 0;
}

Thanks in advance for any hints or examples.

Answer 1

If you take a look at this reference. It states that:

The function returns 0 if key is NOT pressed and value < 0 ( less than zero) when key is currently pressed.

Thus you check for a negative value in order to see if the button is pressed. You can just as easily write it as: if (GetAsyncKeyState(i) < 0) and have it work, with the benefit of it being clearer.