#include 
     
      #include 
      
       #include 
       
        int main(void){   COMMTIMEOUTS timeouts;   HANDLE handle;   DCB dcb;   char buffer[1000] = "abcdefghijklmnopqrstuvwxyz";   DWORD dwLen;   handle = CreateFile("\\\\.\\COM1", GENERIC_READ | GENERIC_WRITE,               0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);   if (handle == INVALID_HANDLE_VALUE)   {      printf("CreateFile() Failed\n");      return 1;   }   timeouts.ReadIntervalTimeout        = 300;   timeouts.ReadTotalTimeoutMultiplier = 0;   timeouts.ReadTotalTimeoutConstant   = 0;   timeouts.WriteTotalTimeoutMultiplier= 0;   timeouts.WriteTotalTimeoutConstant  = 0;   if (!SetCommTimeouts(handle, &timeouts))   {      printf("SetCommTimeouts() Failed\n");      return 2;   }   ZeroMemory(&dcb, sizeof(dcb));   dcb.DCBlength           = sizeof(dcb);   dcb.BaudRate            = 19200;    dcb.fParity             = TRUE;   dcb.fOutxCtsFlow        = false;   dcb.fOutxDsrFlow        = false;   dcb.fDtrControl         = DTR_CONTROL_ENABLE;   dcb.fDsrSensitivity     = FALSE;   dcb.fTXContinueOnXoff   = FALSE;   dcb.fOutX               = false;   dcb.fInX                = false;   dcb.fNull               = FALSE;   dcb.fRtsControl         = RTS_CONTROL_ENABLE;   dcb.fAbortOnError       = false;   dcb.ByteSize            = 8;   dcb.Parity              = ODDPARITY;   dcb.StopBits            = ONESTOPBIT;   if (!SetCommState(handle, &dcb))   {      printf("SetCommState() Failed\n");      return 1;   }   while (! _kbhit() )   {      printf("W");      if (!WriteFile(handle, buffer, 40, &dwLen, 0))         printf("\rWriteFile() returned %d\n", GetLastError());      printf("R");      if ( !ReadFile(handle, buffer, 100, &dwLen, 0) )         printf("\rReadFile() returned %d\n", GetLastError());   }   printf("\nDone!\n");   CloseHandle(handle);   return 0;}