why output will not be shown in c language if we use << instead of <?

Question

why output will not be shown in c language if we use << instead of <? I was reading a book and there it was written but without any explanation..

Answer 1

In c, output is given by "printf()"
In c++, output is given by "cout << "
As c++ is an advanced version of c (with oops) so you can use printf in c++ too by including cstdio library
"<<" is also a bitwise operator.
whereas "<" is a binary operator (comparison).