GUI64 – GUI for the Commodore 64 running on top of the built-in ROM

GUI64 is a graphical-style interface for the Commodore 64, first released in 2024. It runs on top of the computer’s built-in Kernal rather than replacing it with a separate operating system. Despite its windows, buttons, and menus, it uses text mode and character-based graphics, so windows align to the screen’s 8-by-8-pixel character grid rather than moving freely pixel by pixel. Users can choose a Windows-like layout, with a bottom taskbar, or a Macintosh-inspired design, with menus across the top. The desktop holds drive icons rather than file icons; windows can be moved, minimized, and restored, and dialogs keep input focused until they are closed.

The interface supports a mouse, joystick, and keyboard, and provides file browsing for 1541, 1571, and 1581 floppy drives and SD2IEC storage. Users can open directories and disk images, including DNP images, browse their contents, and launch programs by double-clicking them. A File menu’s Boot option handles machine-code files without a BASIC launch stub. On compatible Ultimate hardware, GUI64 can browse USB or SD storage, mount disk images, save settings, and show the device’s time; a WiC64 module can also provide the clock. Its main limitation is that GUI64 does not stay running after launching a program, so it must be loaded again afterward. Support for hard drives and other storage devices is unconfirmed.