Why mvprintw works only after getch?

mvprintw/mvaddch (pdcurses) print text only after getch() (even if it is not connected in any way and the getch is in detach thread).

A question from a different angle: How can i use mvprintw() in a detach thread without getch() for loop print? (A small rendering engine or something like that) //EDIT

// MAIN WHILE() (Strong simplification for debug)

do
	{
		//printf(" [%d] ", exit_flag);
		char player_action = getch();
		
		//render_player_info();
		
		//printf("%d ", player_x);
		mvprintw(1, player_x, "%d ", player_y);
		mvaddch(1, player_y, 'C');
		
		//Sleep(1);
	}
	while(exit_flag == 0);

// CODE BLOCK FROM LAUNCH FUNC (Main while() start after thread detach)

int res;
	
	pthread_t thread_render_engine;
	
	void *thread_func_render_engine(void * arg) 
	{
		int count = 0;
		
		do
		{
			count++;
			printf(" F%d ", count);
			mvprintw(count/10 + 1, count, "P");
			mvaddch(count/10 + 2, count, 'A');
			
			render_player_info();
			
			Sleep(1000);
		} while (!exit_flag);
		
		pthread_exit(NULL);
	}
	
	res = pthread_create (&thread_render_engine, NULL, thread_func_render_engine, NULL);
	
	if (res != 0) {
		mvprintw(29, 0, "main error: can't create thread, status = %d\n", res);
		exit(-10);
	}

	res = pthread_detach(thread_render_engine);
	
	if (res != 0) {
		mvprintw(29, 0, "main error: can't detach thread, status = %d\n", res);
		exit(-11);
	}

I tried to delete getch form amin dowhile and default printf working without getch, but not mvprintw/mvaddch

After you've called functions like mvprintw() and mvaddch() to modify stdscr, you then call refresh() to update the display (getch() does this as a side-effect).

curses doesn't update the window immediately because this way the number of cursor movement operations sent over a (possibly slow) terminal connection is minimised.