Mine

#include <windows.h>
#include <stdio.h>

int main()
{
	MSG msg;
	HWND hwnd = FindWindow("Notepad",NULL);
	     hwnd = FindWindowEx(hwnd, NULL, "Edit", NULL);  // Who uses more than one variable for this? Tut tut

	if(hwnd)
	{
		ZeroMemory(&msg, sizeof(MSG)); // Thus we art lazy.
		msg.hwnd = hwnd;
		msg.message = WM_KEYDOWN;
		msg.wParam = 65;
		
		printf("DispatchMessage next...\nPress Enter...\n%i",msg.hwnd); // %i will show the hwnd btw
		while(!GetAsyncKeyState(VK_RETURN)) Sleep(10);

		DispatchMessage(&msg); //Fail to send "A" to Notepad...

		printf("\nPostMessage next...\nPress Shift...\n");
		while(!GetAsyncKeyState(VK_SHIFT)) Sleep(10);

		PostMessage(hwnd,WM_CHAR,65,0); //Sends "A" to Notepad...

		printf("\nDone!\nPress Escape...\n");
	}
	else { printf("Notepad not found!\n"); } // wtf

	while(!GetAsyncKeyState(VK_ESCAPE)) Sleep(10);
		return 0;
}