Notes about the GUI file extension:
To open this file type, a required software must be installed. Without it you only see a Windows message "The following file cannot be opened
" (Windows 7) or "How do you want to open this file?
" (Windows 10) if you double-click the file. There click on "More apps"
and choose a suitable software to view such files on your PC or from email attachments.
The GUI file type is primarily associated with 'Doom' by Id Software, Inc.. Doom is a computer game by originally written by id Software in 1993. It is considered a landmark title in the first-person shooter genre. It is widely recognized for its pioneering use of immersive 3D graphics, networked multiplayer gaming on the PC platform, and the support for players to create custom expansions (WADs). This file provides menus and HUD in Doom 3 engine-based games.