While writing // delimited comments, it is possible to make a typographical error that affects their expected operation. If one types:
int x =20;// Why did I do this??/
The / at the end was a typo but now will get interpreted into \. This is because the ??/ forms a trigraph(opens new window).
The ??/ trigraph is actually a longhand notation for \, which is the line continuation symbol. This means that the compiler thinks the next line is a continuation of the current line, that is, a continuation of the comment, which may not be what is intended.
int foo =20;// Start at 20 ??/int bar =0;// The following will cause a compilation error (undeclared variable 'bar')// because 'int bar = 0;' is part of the comment on the preceding line
bar += foo;