In 1968, the Motion Picture Association of America (MPAA) introduce the X-rating to classify movies depicting adult-only content, usually entailing explicit language and sexual activity. Choice of the X, apparently, evoked the letter’s association with the word explicit or symbolic use for restriction. Brian De Palma’s Greetings, the debut film of Robert De Niro, was the first film to be rated X. Additionally, some are using .ii, .ixx, .ipp, .inl for headers providing inline definitions and .txx, .tpp and .tpl for template definitions. Those are either included in the headers providing the definition, or manually in the contexts where they are needed. In the 1970s, the adult-film industry embraced the X-rating, with producers using XXX to market a film as especially wild and sexy. Triple X’s came to mark, if not advertise, other products and services (e.g., strip clubs, magazines) as pornographic, a practice which carried into online pornography in the 1990s.

Rajasthani bahu desi stepdaughter resembling her big breast and press stepfather indian latina body beautiful night approximately simmpi Sexy Teacher StarSudipa and Fresh Young 18+ Boy play a Sex Relaxation When No One at one's disposal Home Full Glaze Quenched his lust by having an illicit relationship with an 18-year-old girl who was as delicate as a flower Headers have used the corresponding .H, .h++, .hh, .hxx and .hpp. But unlike the main files, .h remains to this day a popular choice for C++ even with the disadvantage that it doesn't allow to know if the header can be included in C context or not. Standard headers now have no extension at all.

Historically, the first extensions used for C++ were .c and .h, exactly like for C. This caused practical problems, especially the .c which didn't allow build systems to easily differentiate C++ and C files.