How does Wikipedia handle URL's such that “http://en.wikipedia.org/wiki/TCP/IP” is possible?

Question

Notice the slash in "http://en.wikipedia.org/wiki/TCP/IP" How does it not misinterpret TCP as a subfolder?

Answer 1

It has an .htaccess rule that spots the /wiki/ and interprets everything after that as a parameter to be passed to a PHP script, a bit like this:

/pagedisplay.php?page=TCP%2FIP

Note that the slash gets converted to %2F.

This happens behind the scenes so you don't see the url being rewritten.