[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.