On most systems, the way to invoke Octave is with the shell command `octave'. Octave displays an initial message and then a prompt indicating it is ready to accept input. You can begin typing Octave commands immediately afterward.
If you get into trouble, you can usually interrupt Octave by typing Control-C (usually written C-c for short). C-c gets its name from the fact that you type it by holding down <CTRL> and then pressing <c>. Doing this will normally return you to Octave's prompt.
To exit Octave, type quit, or exit at the Octave prompt.
On systems that support job control, you can suspend Octave by sending
SIGTSTP signal, usually by typing C-z.