COMX File
What are COMX files and how to open them
Are you having problems opening a COMX 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 COMX files.
What is a COMX file?
A .COMX file is a COMX-35 Program file.
A COMX-35 Program file stores a program written for the COMX-35, a home computer built around the RCA CDP-1802 microprocessor. These files contain machine-code or BASIC program code that was originally saved (for example, from cassette tape) or transferred by the SuperBoard expansion or through an emulator so that the program can later be loaded into the computer or in an emulator that replicates its environment.
Such programs are created by either end users entering BASIC or assembly language on the COMX-35 (or building an add-on board like the SuperBoard), or by tools that convert and save code in the format used for COMX-35 loadable software. Once saved, they can be loaded back into the system, or into emulators like EMMA 02 that support the COMX specification.
The format includes a header used by COMX-35 hardware or its emulator shells. The header contains a signature at the very start: the ASCII string "COMX" beginning at offset 1 (that is, the first byte after the file position-0) serves to identify these files.
How to open COMX files
Important: Different programs may use files with the COMX file extension for different purposes, so unless you are sure which format your COMX 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: September 2, 2026
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