 Residents, continuing with the previous module, in this module we will discuss that what happens when you click on a link and what are the corresponding commands when the data is sent to the server and what are the different parts of the URL. So all those nitty-gritty details will be discussed in this module. So let us start with the outline of the module. So in this module I will talk about the HTTP header and what are the HTTP actions which are the post and the get actions and then what are the different parts of the URL. There are six parts of the URL which we will briefly talk about and how do we send the data. What are the pros and cons of sending the data using part of the search part and sending the data as part of the message body and what are the pros and cons of that things details will be discussed in this module. So let us go into more details. So we have whenever you click on a link, whenever you type a URL in the text box of the browser or a command is executed, what is happening at the back end, what is happening in the background. Right. So we have a message. We have a message and that message has a header and that message has a message body also. So where does that message comes from? Now that message comes from the web server. You are sending a command and the server responds. So the server responds based upon the command which was sent. Now it may happen that there is no message from the server. So that message then is generated from the client side also. So what are you are seeing technically on your screen is a message. Now that message consists of three parts. These are the three parts of the message. It consists of the action. It consists of the URL. This URL itself consists of six parts and the HTTP version also. And then of course is the message body and the response. Now most of these things are written in the web log along with the version of the browser also. So what are the action? Now action, there are two types of actions which are the get and the post. So what is the get up generated web page? Okay. Now this web page is a dynamic web page and this web page is generated by the web server. So the get action results in asking the web server to generate a dynamic web page. I think it is clear now. And then is the post action in this module and in the coming modules we will be going into more details about the get and the post action. The post action basically is a transfer. It is used in the submission of a form also. It could be audio. It could be video and so on, right? So we will of course go into more detail and the things will become clear. So post action is mostly involved in submitting a form. What is in a form that we will be discussing very soon. So parts of the URL as I mentioned the URL consists of six parts. So we have this scheme HTTP and this is followed by colon and two slashes, right? And then is the host name. The host name is that from where or what is being referred to that host name could be for example, www.yourdomain.com, okay, data to be a dot base CNN.com or it could be an IP address. If it's an IP address, it could be consisting of it's basically alphanumeric. So we have those numbers, four sets of numbers and a dot in between. Now when the communication takes place, that communication takes place over a port. And that port has a default value of 80, which is written over here. And of course, depending upon the nature of the application and depending upon how the application has been developed, that port number can vary. But the default value is 80, okay? Now when we are referring to the resource, that reference is based upon is identified using slashes, forward slashes, okay? Now if the resource being referred is on the local computer, the computer on which you are working, for example, you are developing a website and you are testing it on your local machine, so the reference is on your local machine. So once you are satisfied with what you are developing in terms of performance, in terms of results, then of course, you can move or port your application to the web server. So when you have it application on your local machine, then these are three slashes. And then is a path component. So when nested inside the directory of your machine, your resource lies, then you use this path component. And of course, the data which is sent to the web server, the data which is sent to the web server, okay? And corresponding to that data, the web server generates a response, okay? So now we go into the message body, okay? Now when you send the command to the web server, you need to send maybe additional information to the web server, additional data to the web server. And that additional data and information is part of the message body and it can be part of the URL also. When it's part of the URL, it is the search part, okay? In the search part, the type of data is usually text or it is numbers, okay? And you may be passing multiple values. And those multiple values are shown or separated by an m% sign, as I've shown on the screen, right? And remember one thing, whenever the action is the get, the data is always sent in the search part. Now, using the get action has its own limitations and issues, which I'll show you in the next slide. So when you use the get, the data is visible. You may have seen the data which is passed with the URL, with the question mark also. So when you can see the data, it has security issues. And one can actually change the data, somebody, malicious user and create problems, okay? The other limitation of using the get action is you can only use text data. Now, although you can send out of data with the get action, right? But there are certain browsers which have issues handling large text in the get action. So the other option is the post. There are many benefits of using the post. One of the benefits is the security. Data is not visible. Whatever is being sent, okay, from your browser to the server, that is not visible to the users, which are the client end. And you can send multi-media data, you can send multi-part data, you can multi, you can put multi with many, many things. So all that data is passed using the post action in the message body. And finally, you can work with usually long messages, usually long message bodies. So depending upon the application, right? You may use get or you may use the post action. So in the subsequent modules, we'll talk more about these two actions. So that is all for this module. Thank you very much.