What language are we talking about?
It's worth sharing some code to give you better and more accurate answers.
In general, many languages allow you to print to the standard output continuously. If you want a line break, you have to do that deliberately.
In C you would do this:
const char * myString = "Hello World!";
%s means you want to print a string (provided as myString) then it is followed by \n which denotes the new line character.
In C++, you'd rather do this:
std::cout << myString << std::endl;
where std::endl denotes the new line character(s) (depending on the platform you're compiling the code).