console

console 
    traditionally physical input/output device =  teleprinter 
    provides a way for the kernel and other processes to 
        receive text input from the user, typically entered with keyboard 
        send text output to the user, typically on a computer monitor

     teleprinter = tty 

    console listens on stdin for character input and sends to shell or program running in shell

Linux system console 
    internal to the Linux kernel
    the device which receives all kernel messages and warnings and which allows logins in single user mode

    two main implementations, differ in how to draw characters
        legacy text mode
            works with VGA and previous video types
        current framebuffer
            graphic hardware-independent abstraction layer
            able to show graphics, eg logos while booting

virtual consoles 
    consoles that are logically separate, but which access the same physical keyboard and display
    created after boot complete, each runs a getty process which runs /bin/login

terminal emulator
    program that emulates a video terminal within some other display architecture
    in graphical env, listens for mouse input which it encodes in byte sequences and passes on to stdin of shell or programming running in it.
    does not understand mouse input, only useful when passed on to ncurses app which can process it.

textmode virtual terminals (teletype terminals - tty's)
    Ctrl-Alt-F1 etc.

Pseudoterminal PTY
    under ssh, local to machine but creates slave terminal on remote machine

Job Control
	suspend command puts shell in background, but can't suspend a login shell


Terminal Control
	\[     begin a sequence of non-printing characters, which could be used to embed a terminal con­ trol sequence into the prompt
	\]     end a sequence of non-printing characters

	stty 
		commands for changing size, colours, correcting hung terms .
		-a				List control characters
		cols/rows #		Change width/height of terminal
		sane Ctrl+J		Reset hung terminal

	setterm	 Control colors, power saving etc.
	xset	 Similar, in x

Terminal command keys
	^V + control char	send contro char + sequence to driver literally			
	^V ^[			Start a terminal command (xterm or 'linux' console)	
	^C			interrupt
	^D			end of file
	^W			kill (erase) word
	^U			kill (erase) line
    ^s          Stop output
    ^q          Resume output

Virtual Terminals (tty's)
	S Pg up & Pg down	Screen up and down in terminal screen
	Left M+ lr arrow keys	Cycle through virtual terminals
	kbd_mode -a		Reset keyboard for all consoles to ASCII mode

Secondary Prompts
	shown after delete newline (\), open quote (' or "), or a pipe (|)