 Welcome back, in the previous segment we discussed namespaces and the using directive. This segment we are going to talk about how we can use C++ without simple CPP and we will also conclude this entire lecture sequence. So how do you use C++ without simple CPP? If you want to use it without simple CPP, first of all you will not be able to do graphics, but that is not all. When you write hash include simple CPP, that itself includes the following lines for you. So it includes a line called line which goes hash include IRO stream and also a line which goes hash include CMath and it also includes this line using namespace std. These lines are useful. The names in cout and endel all related to input output are defined in the namespace std and this definition happens in the standard header file IRO stream. So therefore you need to include IRO stream so that you get these names and if you want to use them directly without having to write std colon colon cn, you also need to have this line using namespace std. So if you do not include CPP, if you do not have this line, then you should have all these lines and you should have the line CMath because if you want to use functions like square root and all of that, square root sign apps, whatever. So let me give a very simple example of how you can use C++ without simple CPP. So you might say hash includes IRO stream using namespace std, end main, end n, c in n, so read n and say print out its cube. So this could be a really simple program which you could write without having to use the simple CPP features. But because simple CPP was including these things and because you need to use cn and end l, you need to have these lines. Here is another way of writing the same thing. So you could write IRO stream, end main, end n and now because you did not write namespace std, you will have to write std using namespace std, you would have to write std cn and not just cn and likewise std colon c out and even std colon end l. So that is basically how you are going to use C++ without simple CPP and of course had you needed to use any math functions you would also have to include hash include c math. So just to make sure, just to persuade you that this works, I am going to show you both of these programs and run them. So this is the first program that we saw where you are using, you are not including simple CPP but you are including IRO stream and you are using the namespace std and you are writing the program. So let us compile it, we can compile it with S++ still but we can also compile it with the basic C++ compiler and that is called g++ on Unix. So I can compile without simple CPP, so it has done its job, so it expects me to type in a number, so let us say I type n9 and indeed it is printing out the cube of 9 which is 729. Let me show you the other program without simple CPP 2 it is called and here I have not put in the line using namespace std but instead I have included the prefix std colon colon before all the names which are belonging to that namespace std. So again let me compile that, so S++, so I could compile it with S++ as well but I could compile it with g++, let us use g++ again because that is what you would do if you are not using simple CPP, so without simple CPP 2 dot CPP, so it is compiled dot slash a dot out, again it is expecting me to give a number, so let us say I type 7 and yes the cube is 343, so that is done. So if you wish you can run your programs without using simple CPP but then you would have to type these lines and if you are feeling tired about typing these lines you can continue to use S++, no it will work anyway. So that concludes the part about how to use C++ without simple CPP and specifically what include files you need to use. Now I want to conclude this entire lecture sequence on how to write large programs. So the first point that we made are functions are building blocks of programs. So just as when you write a book you typically break it into chapters, if you are designing a device you break it up into subsystems, systems and subsystems, similarly when you are writing a program you kind of break it up, break it down into functions, there will be other things that will also come up but we will talk about those later. Functions can be put into many files provided each file contains a declaration before the use of the function. Declarations can go into header files, it is convenient if you put declarations into header files and when you put declarations into header files there are some additional details which you might want to learn if you use really if you yourself try to write really large programs. Some of these details are discussed in the book. Functions can be put into namespaces and you do have some namespaces which are defined as a matter of as a standard by default in C++ and the namespace std is one of those namespaces. So different programmers can put their work in different namespaces and the same name may be defined in many namespaces. So in fact this says that you could have a variable called cn in your program. I would recommend that you do not do that because you will confuse yourself but in principle you could do it because the cn that you are using so far is a name defined in the namespace std. So if you carefully want to differentiate it and put cn in your own namespace that is possible. But again as I said not recommended. The details of all this are discussed in the book and that concludes this lecture sequence. Thank you.