Where did these examples come from? I just printed out the whole site of: en.cppreference.com.

Well, maybe you ask why am I doing this stupid work?

First I needed to learn English language, second I needed to learn 10-finger-type
and third I liked learning programming. So I do all three of them together. And I
typed these examples to improve my EN language and TYPING and C++ programming.

I tested all these examples with this command-line argument:
g++ -std=c++14 -O2 -Wall -pedantic -pthread

On Gnu / Ubuntu 16.01 LTS and code::blocks IDE 16.01 (32 bit)

If you are confusing with my examples, I apologize to you.

You can see the major reference sites:
1️⃣ en.cppreference.com 2️⃣ cplusplus.com
3️⃣ msdn.microsoft.com

compiler:

operating system:

how many way do you know for "hello world" in C++?

#include <iostream>
#include <sstream>
#define HW(...) std::cout<<"1:\t"<<#__VA_ARGS__<<std::endl;

int main(){

	HW(hello world!);

	std::cout<<"2:\thello world!"<<std::endl;

	std::operator<<(std::cout,"3:\thello world!")<<(std::endl);

	endl(std::cout<<"4:\thello world!");

	std::cout.put('5')
	         .put(':')
			 .put('\t')
			 .put('h')
			 .put('e')
			 .put('l')
			 .put('l')
			 .put('o')
			 .put(' ')
			 .put('w')
			 .put('o')
			 .put('r')
			 .put('l')
			 .put('d')
			 .put('!')
			 .put('\n');

	for(const char* hw("6:\thello world!\n");
		*hw!='\0';
		std::cout<<*hw++);

	[]{std::cout<<"7:\thello world!\n";}();

	std::istringstream("8:\thello world!\n")>>std::cout.rdbuf();
}

output

1:	hello world!
2:	hello world!
3:	hello world!
4:	hello world!
5:	hello world!
6:	hello world!
7:	hello world!
8:	hello world!

How about obfuscation a code?

#include                         <iostream>
#include                          <sstream>
#define                            HW(...)\
std::cout<<"1:\t"<<#__VA_ARGS__<<std::endl;
int main(){HW(hello world!);std::cout<<""""
"2:\thello world!"<<std::endl;std::operator
<<(std::cout,"3:\thello world!")<<(std::endl
);endl(std::cout<<"4:\thello world!");std::
                  cout
                .put('5')
                .put(':')
                .put('\t')
                .put('h')
                .put('e')
                .put('l')
                .put('l')
                .put('o')
                .put(' ')
                .put('w')
                .put('o')
                .put('r')
                .put('l')
                .put('d')
                .put('!')
                .put('\n');
for(const char* hw("6:\thello world!\n");*hw!=
'\0';std::cout<<*hw++);[]{std::cout<<"7:\the"
  "llo world!\n";}();std::istringstream("8:"
   "\thello world!\n")>>std::cout.rdbuf();}

output

the same as above