The beep and flash routines are used to alert the user.
The beep sounds an audible alarm, if possible; otherwise it flashes the screen.
Flash flashes the screen, and if that is not possible, sounds the alert.
If neither is possible, nothing happens.
Nearly all have an audible alert, but only some can flash.
These functions are described in the Curses standard.
Found poem (erasure) from the Linux Man Pages. Complete text at: