The backslash (
\n is a newline character (rather than a backslash followed by the letter n).
In order to output a literal backslash, you need to escape it. That means
\\ will output a single backslash (and
\\\\ will output two, and so on). The reason
"aa ///\" doesn’t work is because the backslash escapes the
" (which will print a literal quote), and thus your string is not properly terminated. Similarly,
"aa ///\\\" won’t work, because the last backslash again escapes the quote.