Why are there digraphs in C and C++?

Question

I learned today that there are digraphs in C99 and C++. The following is a valid program:

%:include 

%:ifndef BUFSIZE
 %:define BUFSIZE  512         


        

Answer 1

I believe that their existence can be traced back to the possibility that somewhere, somebody is using a compiler with an operating system whose character set is so archaic that it doesn't necessarily have all the characters that C or C++ need to express the whole language.

Also, it makes for good entries in the IOCCC.