 Hello and welcome back. In the previous segment, we talked about how we can compose maps and vectors and strings together to build interesting data structures. In this segment, I am going to talk about somewhat technical, somewhat syntactic, called the type def statement. And then I am going to conclude this sequence of segments, so type def. So let me first observe that type names can become very long and cumbersome to write. So for example, we have already seen that that fair table that we constructed had this type. So we have to write it when we define that variable. But now suppose I want to pass that variable to a function, then even there we will have to type this as the type of that argument. So you may think that look typing this again and again is very cumbersome and also it does not really tell me what this is all about. So basically a type def statement allows short forms to be defined and the idea is this. So I write type def, then I want I write the type for which I want to create a short form and then this is the short form. So for this I could have written something like this, I would say type def and this is the type, this very type mentioned over here and for that I am going to create the name called fair table type. So this is the type and this is the name that has been created, this is the synonym for this long type name. And how do I use it? Well exactly as you would think I can write fair table type, fair table. So this creates a variable named fair table of this type. Actually in the last example I called it fair but since it really is a fair table maybe I thought I should use this full name. So just to complete I could write fair table Mumbai Pune equal to 500 or see out fair table Mumbai Pune. So that concludes the discussion about type def. So let me now make some concluding remarks about this sequence of segments. So let me ask the question to you, do we need data structures such as vector, strings, map, sets or could we live without them? Well we can live without them. So they are not strictly needed. In fact the language like C does not have these data structures. And what is done there? Well the programmer has to really use arrays and write code to implement insertion, finding etc or some other kinds of constructs that the programmer himself or herself has to create. So these data structures or these classes are strictly not necessary but are they useful? You bet, they are amazing, they make it very easy to write code. So the designers of these data structures have guessed and they have guessed very well what kinds of things people want to do and they have put them into these data structures. And furthermore these data structures are template classes. So you can instantiate them with any type. So you can create a vector of ints, you can create a vector of doubles, you can create a vector of circles, you can create a vector of vectors as we just saw. So all of these things are possible. So whatever type data structure you want that will get created and it will reduce chance of errors. So because all these data structures have been created by expert programmers and they have been tested. Not just by those programmers but because they have been released to the entire world, the entire world has tested these data structures for you. So they are unlikely, it is unlikely that there is any error in them and they are so compact that using them is also very convenient and unlikely to produce errors. And of course they make programs small. So whatever your logic is, you can see it often in a glance that look this is what I am doing instead of having to go over several pages of code. So it makes for improved program readability as well. So definitely use them. So that is the main message of the program and that is the end of this lecture. Thank you.