The origin of the IDX format supported by DC2N5-LC, Ultimate-64, etc

I have been made aware of claims that the IDX format has its origins in somebody else’s work and they were not credited for their original idea.

Let me put the record straight: this claim is inaccurate. In pretty much all fields of human research there have been discoveries and inventions that were made independently by people across the world. The IDX format invention was no exception.

Here’s the background story around this specific one.

The IDX format as supported by DC2N5-LC, C2NEmu, TAPClean FE and Ultimate-64 was drafted by Gideon Zweijtzer (Ultimate-64) and Tom Roger Skauen (TapEx). I was pulled in the discussion for reviewing the format: it made sense, given my background in the 8-bit tape community (TAPClean FE, various DC2N versions, C2NEmu).
The format seemed sensible as it was proposed to me, so, in the end, I mainly contributed the suggestion that offsets in hexadecimal should be allowed and start with “0x”.

You might want to check the post I wrote at the time (October 2016) about this subject.

Digging into the points of the claim the original idea was stolen:

  • The file extension, IDX, was stolen.
  • The idea that IDX and TAP need to have the same filename and be in the same folder was stolen.
  • The format of file contents is different, but the concept was stolen.


  • Who would, in their right minds, think of the IDX file extension for an index file? Pretty much everybody.
  • This is a pretty obvious choice: I just don’t see how anything else would make sense.
  • The current format is a pretty obvious choice for an index file: offset and filename entries for each file!

Conclusion: there isn’t a single valid argument in the claim that the format was invented by somebody else who was not credited for his original idea/work.

Gideon, Tom and myself weren’t aware of an existing IDX format at the time we came up with our proposal. One can’t be expected to have to credit others for work they weren’t aware of and which they didn’t use for their own work.

About Luigi Di Fraia

I am a Senior DevOps Engineer so I get to work with the latest technologies and open-source software. However, in my private time I enjoy retro-computing.
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