I was recently talked into taking on the role of the negligent MediaWiki administrator for the esoteric programming languages wiki. As a consequence, I have now a local copy of the XML dump of the wiki contents (that anyone can download). To celebrate Easter in the traditional manner, then, I've spent some time computing statistics of the link graph of the wiki.
Recently, there was some idle discussion on #esoteric on the topic of reserved identifiers in C and POSIX. The discussion further progressed to a thought experiment on whether it would be possible to write useful programs in C if the standard (or POSIX) reserved all identifiers, i.e., using only identifiers defined by the standard, in a legal manner.
The following program is a rudimentary brainfuck (sans input) interpreter that is at least mostly valid C, yet uses no user-defined identifiers (after preprocessing).
This is a gamified extension of the x86 opcode mnemonic generator. Playing should, hopefully, be self-explanatory.