Interrupt commands are commands that are read from the keyboard during
execution of a command sequence. This is only a very limited set.

    - When TV is executing a command, CTRL_T and HELP can function as
      progress indicators. Every time an executing file terminates, or an
      iteration is closed, TV checks if CTRL_T or HELP were pressed. If
      so:
         CTRL_T causes the current line to be displayed in the status-
                display;
         HELP   causes the information usually generated by the  :h -
                command to be shown in the status-display.

    - When TV is executing a command, CTRL_G can be used to abort a looping
      sequence. Every time an executing file terminates, or an iteration is
      closed, TV checks if CTRL_G was pressed. If so, all (possibly nested)
      sequence- and file-execution is terminated, and control returned to
      the user. Any typed-ahead characters will be discarded.

    - When TV is executing a command, CTRL_C can be used to abort the TV
      session. Every time an executing file terminates, or an iteration
      is closed, TV checks if CTRL_C was pressed. If so, all (possibly
      nested) sequence- and file-execution is terminated, no registers are
      saved, and TV aborts.

NOTE: There is a CTRL_X-setting to enable or disable each of the CTRL_T-,
      CTRL_G- or CTRL_C-commands as Interrupt Command.