The clear() and erase() functions clear stdscr, destroying its previous contents. The wclear() and werase()
functions perform the same action, but clear the window specified by win instead of stdscr.
The clear() and wclear() functions also call the clearok() function. This function clears and redraws the entire screen on the next call to refresh(3XCURSES) or wrefresh(3XCURSES) for the window.
The current background character (and attributes) is used to clear the screen.