Question

what is fflush(stdin) in c programming?

Answer 1

It flushes the standard input buffer !

Answer 2

This function is used to flush any data in output stream. So this will compile but its behavior is undefined by the ANSI C standard. The fflush() function is only meant to be used on streams open for output, not input. Both fflush(stdin) and fflush(NULL), in some C libraries, will flush stdout and stderr, but this is completely unportable! Thus, it should not be used.