CJM File

What are CJM files and how to open them

Are you having problems opening a CJM file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your CJM files.

What is a CJM file?

A .CJM file is a TheC64 Config/Joystick/Mode Settings file.

TheC64 Config/Joystick/Mode Settings files store configuration data used by the THEC64 console (and its variants like the C64 Mini) to control how a virtual media file (such as a disk image or cartridge) is run. They allow defining the computer model, video mode, disk access behavior, joystick port mapping, controller button assignments, vertical display shift, memory expansion options, and other emulator settings. These files are plain text settings that THEC64 reads when launching media files, so the system behaves correctly according to the game or application being used.

These settings files are written and saved by users (or device firmware) using a text editor. A config file must reside in the same folder as its corresponding virtual media file, sharing the same filename (but with the CJM extension), so THEC64 matches them and applies the settings. Alternatively, a special file called "thec64-default.cjm" placed in a folder applies its settings to all files in that folder and any subfolders, whenever a file-specific CJM is missing. Settings in a CJM file override filename flags and default behavior.

Settings are given as lines starting with a one-letter code followed by a colon and comma-separated values. For example, "X:" lines define the computer model (such as 64 or vic), video standard (pal or ntsc), display height (fullheight), memory expansion (such as 35k), and disk mode options like "accuratedisk" or "driveicon." "J:" lines configure joystick behavior: which port is primary (marked with *), and mapping of each joystick direction or button to a keyboard key or controller button. "V:" lines set vertical shift to adjust screen position, with different valid ranges depending on hardware model.

In the file's text header, the first character of a line identifies the setting type (for example X, J, V), followed by a colon. The "J:" lines specify ports in the format "J:1:" or "J:2:" where "1" marks the primary joystick port. Values following consist of identifiers like JU (joystick up), JD, JL, JR, JF (fire buttons), SP (space), function keys (F1, F2, etc.), or other keyboard keys. The vertical shift setting "V:" accepts integer values (positive or negative) within hardware-dependent limits.

How to open CJM files

Important: Different programs may use files with the CJM file extension for different purposes, so unless you are sure which format your CJM file is, you may need to try a few different programs.

We have not yet verified any programs for Windows that work with this specific file format. If you know one, please use the 'Suggest a program' link below. Thanks!

Last updated: August 31, 2026

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