Does `cin` produce a newline automatically?

Question

Let's consider the following code:

#include<iostream>

int main()
{
    std::cout<<"First-";
    std::cout <<"-Second:";
    int i;
    std::cin>>i;
    std::cout<<"Third in a new line.";

    while(1){}


}

The output when value 4 is given to i is:

First--Second:4
Third in a newline

cout doesn't print any newline. But after I input any value(4) for i a newline is printed. There could be two possible reasons for this:

• The Enter key I press after typing a numerical value for i is printed as a newline.
• cin automatically generates a newline.

Although the first reason seems more reasonable but the reason, I am thinking 2nd reason could also be true, is because after Third is printed when I press Enter no new line is printed even the program continue to run because of while(1)--which means the console window doesn't print a newline when Enter key is pressed. So it seems like cin automatically prints a newline.

So, why is the newline being generated after I give input to cin? Does cin automatically prints a newline?

Answer 1

The number and newline you entered is printed by the console software. cin won't print anything in my understanding.

Try giving some input via redirect or pipe, and I guess you will see no new line printed.
For example:

$ echo 4 | ./a.out
First--Second:Third in a new line.

where $ is the prompt and echo 4 | ./a.out(Enter) is your input.

Answer 2

Check this out: http://ideone.com/tBj1uS

You can see there that input and output are separated.

stdin:

1
2

stdout:

First--Second:Third in a new line.

Which means, that the newline is produced by the Enter key and is a part of the input, not the output.

Answer 3

If someone will have the same problem, I was able to solve it like this:

string ans1;
getline(cin, ans1);
    ans1.erase(remove(ans1.begin(), ans1.end(), '\n'),
        ans1.end());
int ans1int = atoi(ans1.c_str());

Basically, it works by deleting all the newline characters in the string, and then ,aking it integer or whatever else you need. Also you will need algorithm library for it It's not that elegant, but hey, it works!