The 4 file extension is associated with IBM Embedded ViaVoice, is a range of language-specific continuous speech recognition software products developed by IBM. The current version is designed primarily for use in embedded devices. The 4 files are used for language specific script data.
The 4 file extension is associated with the GNU Screen full-screen window manager that multiplexes a physical terminal between several processes, typically interactive shells for GNU Linux operating system. The .4 file stores log created by the GNU Screen.