[nurettin]

>> C is the lingua franca of programming

I don't have the exact numbers, but this seems debatable.

[Reelin]

It's the lingua franca in that it's the standard for interoperating. Every high level language I've used has had at least one C FFI readily available.

[nurettin]

We do have a mutual understanding on whether C foreign function interfaces are available for other programming languages, which does enable languages to send system requests (for systems which are written in C) or to create optimized C code to parse documents or calculate formulas. I am aware that the concept of making languages talk with C interfaces exist. And I made the above statement knowing this.

[rustybolt]

I think the term lingua franca is most often used to indicate a commonly understood language, not one that everybody actively uses.

Six of the eight most popular programming languages (from https://www.tiobe.com/tiobe-index/) have C-like syntax. I think most people would agree.

Edit: I think that in this context, Reelin's comment is more appropriate: This is not about understanding, but about interoperability.