The cout operator does not insert a line break at the end of the output.
One way to print two lines is to use the endl manipulator, which will put in a line break.
For examle:

#include<iostream.h>
using namespace std;  
int main()  
{
     cout<<"Hello world"<<endl;
     cout<<"I am programmer";
     return 0;
}

Output:

Hello world  
I am programmer  

The new line character \n can be used as an alternative to endl.
The backslash(\) is called an escape character and indicates a special character.

For example:

{
    cout<<"Hello world\n";
    cout<<"I am programmer";
    return 0;
}

Output:

Hello world  
I am programmer  

Using a single cout statement with as many instances of \n as your program requuires will print out multiple lines of text.

{
    cout<<"Hello\n world\n I\n am\n programmer";
    return 0;
}

Output:

Hello  
world  
I  
am  
programmer