The commands exit and quit, as well as the END-OF-FILE character (usually Ctrl-D) terminate input from the current input stream: terminal session, pipe, and file input (pipe).
If input streams are nested (inherited `load` scripts), then reading will continue in the parent stream. When the top level stream is closed, the program itself will exit.
The command `exit gnuplot` will immediately and unconditionally cause gnuplot to exit even if the input stream is multiply nested. In this case any open output files may not be completed cleanly. Example of use:
bind "ctrl-x" "unset output; exit gnuplot"
See help for `batch/interactive` for more details.