Answer 1

You can use them both, but for cout you need to use "<<" manipulator, and for printf you need to use formatter string. It looks like that:

printf("Hello %s\n%c", "World", '!');
/*outputs
"Hello World
!"
*/

%s and %c - formatters, at first program outputs all before '%' symbol, %s says that you need to output string next (in params), when string is outputed then program returns to format string and outputs all until '%' symbol, and %c says that you need to output character (also in params). You can read more about formatters in the Internet, just google it. Formatters also can be composite, like %lc (long character) or %.8f (outputs up to 8 nums after floating point in float or double nums). Hope, I helped you. And sorry for bad english.

Answer 2

no problem, use

#include <iostream>
#include <stdio.h>
using namespace std;

int main() {
printf("hello world");
return 0;
}

Answer 3

Yeah, they just use a different library. <iostream> is standard library for C++ and handles input and output so cout, cin, etc. <stdio.h> is standard C library and also handles input and output as you get printf, scanf, etc..

Answer 4

Yeah I read it on My aunt's book about C. There was #include<stdio.h>. But It was on C language.