Even back in the 1980s, when I was asked to reimplement the heirarchical DEC VMS "help" command for SunOS (in a terminal window), it was necessary to handle individual characters rather than use line-oriented input. The VMS "help" command had been written for VT100/VT200 terminals and their cousins, and was designed to take action on a single key press, rather than waiting for a return/enter action to "send" the command.