 Welcome to the session on latex. So, the entire day today we will cover about latex. So, let us just begin with what are the advantages. So, what is latex? It is a type setting program, especially for mathematical for mathematical documents where there are lot of equations where one has to use various Greek symbols, equations, subscript, superscript, summation sign, integration, derivative, fractions. These are places where latex is extremely useful and there is no second competitor. It is far better than any other one and there is really no need for developing another even in the force. The closest that is there is RST which is also extremely useful, but it is not suited for latex, it is not suited for mathematical documents. So, how long and how long in document can you make with latex? Anything from one page, half page, one page, landscape, portrait, huge books, thousands of pages, there is no limit. One can have headers, footers, I will show you some examples of what examples of difficult things. One can make presentations, the advantages that things written in latex are automatically used in presentations also. So, how do you pronounce latex? Latex, T-E-X, the T-E-X is pronounced like teck in technology or latex, some people also say latex or latex, la, la like in Lahore, latex or latex. So, please do not say latex because even if people know lot of latex, as soon as you say latex, people think this way does not know. As if only pronunciation is the important thing. Of course, pronunciation is nothing, it is not the important thing, but still I request people to say latex. So, important thing is excellent visual quality. One can, it is so called vector graphics, you can zoom in any number of times and still all the curves are extremely clear. So, what is typesetting? So, you do not have to worry about the margins, the spacings, the font sizes. Whenever we have section heading, chapter heading, those font have to be automatically larger. One does not have to worry about them. One can focus only about the content and writing mathematical things is extremely simple. Latex used to be there at a time when people, computers did not have mouse. One can just type in alpha, beta, fractions, just like one types all other text and the plain text is in fact very readable. As readable as, I will tell why the significance of readability, especially for matrices etcetera, it is important that one knows that latex you write in a file and then you compile it, you compile it and then you get the actual document, the PDF file usually. So, here is an example of some big long equation with lot of subscripts with tilde's in the tilde above the particular letter, a transpose subscripts, double subscripts. Here there is this a, let me just zoom in once. So, here there is this a different letter a, I think this is a a for angstrom, only the angstrom one uses capital, but one can use many such, I will show some more examples very soon. So, today we are going to spend time on building a big PDF file, big nodding size number of pages with different features. All these different features we will see one by one. Before we start seeing the outline, these are the various things we will see. Let me just show two more examples, one of relatively complicated mathematical set of equations and another is a presentation also done using latex. So, presentation is done using something called beamer that we will see at the end. So, these are the two things we will quickly see using this. So, let me show an example. Look at this, we can zoom in a little further. So, this is the type of symbols one can get, one can have different, let us see another example here. These are, to write these things are extremely easy. It might look a little complicated now, but once we start, you see all the subscripts, superscripts, this infimum, below that there is this whole subscript and one of these itself has plus, plus as a subscript, one of this itself has plus as a subscript gamma, p, different fonts, p are available. There are for each letter, each letter can be written in plenty number of fonts. So, this is one example. So, let me take some time to show a few more examples. These papers, these PDF files we will put up on Moodle, but these are only examples. Using something called tix, a tix package that is over and above latex, one can for example do such things. Look at this, one can strike out row, column of a big matrix with different colors, all types of colors are also available from within latex. If one wants to, the purpose of explaining this is that there is this particular cross and that is the only cross in this row. So, one would like to strike out that row, that column. This is what typically we do in elimination. In order to explain that, it is very hard, easy to do it on a blackboard. We teachers are used to blackboard so much to write it in a document is extremely difficult. Most of you will agree with this difficulty. Now, these things are very easy in latex using something called tix. So, once one masters latex, there are plenty of resources available for things over this. Let me just show one more example of a presentation. This is an example of somebody else's presentation. So, one can have all these boxes, one can have such things all and please note that all this text that is here for example is all already written up because this is a presentation from a paper and it is already written up and to just put it in a presentation in various blocks is extremely easy to do such shading for example. It is much more easier in latex than for example power point or for example open office. One should keep in mind that for mathematical things, this is the right thing to use and an initial investment of time in learning this is going to come a long way because it is unlikely that latex will become a package that is out of fashion in the next 50, 60 years. So, this is just another example of a presentation that is built using the beamer package on latex. These are all within latex, but using something called beamer. So, let us just quickly see this beamer itself is something we will see in more detail today, but this beamer allows really various complex things. You can have things coming part by part, you can also have something that is growing column by column and how to do it is all there inside this particular beamer guide. This is something I am showing that is available on the net. It is not something that I have prepared, it is already available on the net and exact link etcetera we can put this and also make this PDF file available on the Moodle. We can have different sequence of various things coming on the screen. So, given that all these capabilities are possible both in a document and for a presentation, we will spend the whole of today for learning latex. Let us go to the slides. The first thing we will see is title, author, date, how to write initial part abstract, abstract environment, sections, subsections, appendix, references, bibliography, tables, how to make tables, figures and importantly mathematical symbols, math mode, the so called math mode for equations. You will also quickly see the document that will be produced at the end of this course, at the end of today. First hour we will just see of some basic structure. The next few hours we will see about how to do all this. So, latex is a so called document based markup. You write all this, you write the content in one tech file, one plain text file using an editor and once you compile it, then it creates a PDF file. What we will do today is we will create the PDF file directly. One can also choose to make a PS file, there are other file options also available. So, one can mark various things, one can put comments into the tech file. Importantly there are many features in latex that will allow you to not worry about the overall appearance to begin with. We can focus on the content and once the content is ready, changing the appearance is in case you want to change the appearance from the default appearance, it is very easy to make these changes. So, how do we, so let us get started about this. So, this is the document that we will prepare very soon. We will also see what is the, what is this question mark about. You might say this question mark, not something we like. So, how to create this document is what we will see. So, how to put footnotes, how to have all these numbers, how to have bullets, how to have this table, how to have this matrix, how to have some text. You would have started seeing Python yesterday and very soon you will recognize that this is all Python code here, how to make code come in from another file and that other file might have something that is very normal Python code, but it will suddenly have different effect in latex. How to do those things is what we will start seeing very soon. So, in other words how to import code from another script, how to write all these various symbols, matrices. This entire document at the end of today will be very easy for you all to make, all these maths symbols, how to put Python script come in here with nice colors also. Now, this is appendix till now these were section 1, section 2, section 3. Now, these are appendix, appendices. What would I put the question mark? Notice that I will just latex it once and everything will go away and now all those question marks are gone here, here there used to be question mark. Why the question mark was there and now it is not there, something we will see very soon. So, how to get this references come in here, page numbers of course. What we will not cover is you can get headers, various headers left side, right side, how to put in figures, this particular figure is not being drawn within latex. So, one can draw many pictures within latex, one can have animations within from within latex, animation will be there in the resulting pdf file. This particular figure is generated using Python. So, the purpose of this is that here is this, if you want to explain how this particular Python script generates this figure, if you want to explain that, then you want to write a document and this is an example of such a document, creating which we will cover in today's, in the whole of today. So, we will start how to make part by part, how to make the title, of course, how to set the margins is also very straightforward, page numbers, how to disable page numbers, how to have the page numbers in Arabic numerals, Roman numerals, any other letters instead of numbers, we might want page numbers to come as letters, each of these things are extremely easy. So, please note, in my 15 years of using latex, it is still very hard to say what all is possible in latex, anything that you want, it is unlikely that it is impossible in latex. Somebody or the other would have a contribution about doing a doing a particular thing in latex. So, you all you do is just to look on the net, not just for how to do, whether it is possible, but also about bugs, whether using latex for a particular purpose you are facing this problem, all those things are available on the net, for just like for any other force package. So, how do we do this? So, somebody has asked, please justify the advantage of latex over MS office. So, I am sure that such a question will not have to be answered at the end of today. Somebody has asked me to justify the advantage of latex over MS office, either MS office or open office, the advantage of latex over this will be very clear at the end of today. But of course, we can spend time on discussion about this later today, if it is not yet clear. So, how do you build this? So, let us go to the slides, we are going to write some sample code into a particular file, the recommended extension is tech, dot tech. This is the plain text file in which we will write the content. Once that particular file is opened using a plain text editor, for example, g edit, for example, nano, once it is written in that and saved, then we come back to the terminal to compile. Now, we come back to the terminal and we type PDF latex filename, filename dot tech that is a recommended extension. And to do this is called compile, what does compile mean? Compile means that after you have written the content in this particular tech file, that particular tech file is in a particular directory, you come back to the prompt, you come back to the terminal, you should be in the same directory and then you will type PDF latex filename. Once you do that, then it will produce the output, the default output is draft dot PDF. It will, what PDF latex will do? It will remove, see that this is just an extension, tech extension and it will replace that with PDF and the file will become draft dot PDF. If your original file was madhu dot tech, then this will become madhu dot PDF. So, note that off late we have been using PDF latex, but the same tech file, if you have written the same tech file and you want not a PDF file directly, but you want something called DVI. In the past there used to be this DVI file, DVI I think stood for device independent file, but then when you just do plain latex, it creates something called a DVI file. There are certain advantages for example, PS, there are many things one can do with PS files, PS tricks is some extremely versatile package that is accessible only from latex. So, as far as we are concerned for all basic things, the tech file is the same whether you are going to do PDF latex or latex. If you are using something called a Kyle editor or MiGtec, then latex and PDF latex are just two different icons. The same tech file can be compiled either using latex or PDF latex. For some extremely advanced things only it matters whether which one you are using, certain small certain features may not work in PDF latex, it might work only latex. Certain other features like hyperref linkings within the file, from within the file you might want to click and go suddenly to a browser. These are some things that are currently there only in PDF latex. I would like to say today no need to discuss about which one is better. They both are equally good for all the things that we will see today. For the for several years it will not matter which one of these you are using, why because the advanced things come only later. So, now let us open one such tech file and start putting the content in. So, important is that everything all these commands that you type in latex, they are all case sensitive. Capital or small makes a very important difference. Then there is something called a command. All what are these commands? Every command begins with a slash. So, this particular slash is called backslash. Backslash meaning the one that starts from above comes down. I think last time during the lecture we had told oppositely. So, this is what we will call backslash. This is the slash that one uses most in latex. In fact, in my particular keyboard I have mapped this slash to a symbol that is easier to type. So, this symbol one types again again. Then there are so called various environments. For example, if you want to number various items 1, 2, 3, if you want to bullet them, these are all so called environments which always start with begin environment and end environment. The name of the environment we will see very soon. The entire document itself ends by typing slash end document. Whatever you type after that is ignored. That is not going to be compiled. How do you type commands? Anything that is on each line, on each line, anything that is written after the percent symbol is a command. How do you get the percent symbol itself? Those are things we will see very much. But, percent itself means whatever on that line after that percent symbol is a command. Another percent symbol will also not be read. One percent symbol is enough. Then all these characters are very special. Tilda, hash, not the round bracket itself, everything that is inside the round bracket. They have some special meaning. What those meanings are dollar, this hat of course, suggests superscript. That is indeed superscript, ampersand has some other meaning. Curly brackets, curly brackets have their own meaning. Round bracket have no meaning. So, whatever is inside this round bracket has some special meanings. Now, you might want that symbol itself. In that case, you should just put a slash before it. Then later you will understand that you actually want the dollar sign itself. So, then dollar will not become a command. It will not be a special character. So, slash symbol, how do you get the slash symbol itself? If you want a slash symbol, you cannot put another slash before it. For that one should just type text backslash. It is unlikely that we require this, but then if you want it, slash backslash will also give you the symbol. Before we see more about this, we should open a tag file and compile it and see. So, why do not I open this? This is a tag file that I have opened. So, this particular tag file already has some information. So, first thing that we will do is, we will put a slash end document. This was the tag file when we compiled we saw the output. We saw something about psi pi. So, why do not we what I have done in this particular place I have put slash end document. As soon as we do this, I have written that. How to write it? That depends on the editor. If you are using some other editor, each editor will have its own way of writing all the information into the file. So, once it is written, so pdf latex, this is a command. On my prompt I have typed pdf latex glimpse at psi pi dot some lot of information has come on the screen. Once it has come on the screen, once the prompt has come back. Please note, we typed this and we pressed enter. Some information has come on the screen, but finally the prompt has come back. Whether the prompt has come back or not, always you will pay attention. This is one thing that is missing in Kail. In Kail, there might be a different way of coming to know that latex has ended without any errors, whether you have successfully finished latex king or not. So, as far as our discussion is concerned, latex king is same as pdf latex king. They are the same. I said as far as they are concerned, they are the same. There is no important difference between them. So, when we type pdf latex glimpse, this is the name of the file. We have come back to the prompt. Whether it has come back to the prompt or not, each one of you will always pay attention. That should be the top thing on everybody's mind. So, I recommend that you all get used to compiling from the command prompt. While later on you might decide to do Kail, you should keep in mind that this command prompt has its own advantages. What its advantages are? We will see very soon, but right now we are concerned whether latex ends and you come back to the prompt or not. I will very soon give you an example where it does not come to the prompt again. But right now it has come to the prompt and let us see, let us open that document whatever we edited just now. So, here this is the document that has got created and notice that after the abstract we had put one end document. So, the rest of it has got ignored. Now, how to get this title, etcetera, we will see very soon. But this is the pdf file that has got generated because we compiled. When we compile, this pdf file gets generated and when you have already opened that same pdf file using events, whether events will automatically update and while you are viewing this, you might, you might steal thilly, you might very hidingly go and again change the pdf file. You might latex it again, whether this events will refresh or not, that depends on the pdf viewer. I should say most pdf viewers indeed will refresh, but whether they refresh or not is not the problem of pdf latex. It is not a problem of latex. It is something about the pdf viewer. For integrated environments like Kyle, I am sure it will refresh. That is what is integrated about it. Here we are doing some separate things. We are using, we have opened that file using vi editor here. Once we are writing the various things, we can quit out of here, come to the prompt and then we can type. These are two, three separate things. We have first written the content into a tech file using a plain text editor. For example, when? For example, g edit, for example, nano. This is some completely up to you, which editor you want to use. So, most people, many people use emacs. After this editing has been done, after you have written the file, written the file to which file that you should know when you are opening the editor. We have written it all to this particular tech file. Once that is done from the command prompt, you will type pdf latex. pdf latex, that particular file name. So, all this pdf latex has compiled and generated a pdf file. It says, at the bottom it says, output return on glimpse at scipy.pdf. This is the pdf file that has got generated just now. If you want, you can do ls minus alrt. That will show you the recent most file and it will indeed be this pdf file. The log files, these are all generated together. They will all have the same recent most time stamp. Now, this particular pdf file is going to be viewed using a pdf viewer. That is a separate program. You might have a pdf file that they take in generate, pdf latex didn't generate. Somebody else gave you a pdf file. How do you view pdf files? Evans is an extremely good viewer for viewing pdf files. There are many document viewers, many pdf file viewers. This is one amongst them. We are opening that particular pdf file using Evans. So, these are three separate things. Whether the pdf viewer will refresh the file depends on the pdf viewer you use. If you use Evans, it will refresh. So, if this particular document has only one page, not even one full page, it has only the top. How did we get this title of the document? This particular part is the author of the document. As we already said, I happen to be only sitting here and presenting it, but the entire contents of this SDS course has been contributed by all of our FOSI project employees. They are playing a very key role now also for all the evaluation work, all the model help. I happen to be only a face here for the instruction purpose. So, let us go back to the slides. So, what we already saw was that percent symbol, anything after that is the comment. There are these special symbols, tilde, hash, dollar. These are all special. They are special. What is their effect that we will start seeing very soon? If you want these special symbols now, then you just put a slash before it. Whether they are special or not, no need to remember. When you see your pdf file, you will see that dollar I wanted, it has not come, whereas dollar is special. Sometimes the pdf file will not even get created because there is an error. You will not end with the prompt because these, this dollar symbol, for example, if you put and you do not put it, you do not put another dollar symbol, then there will be an error and you will not come back to the prompt. So, for now, you will always pay attention whether you have come back to the prompt or not. If you want the slash symbol itself, we will use slash text backslash. This is what we already saw. This is all inside the tech file. What does the slash slash do? Why can you not put a slash before the slash and suddenly you will have the slash character? That is because double slash, double backslash, it inserts a new line in the output. A new line gets created and that is why you cannot escape the slash by another slash. If you have empty line, one whole line that has nothing, that has only spaces. If you have a line in your tech file, entire line has nothing or spaces, then that marks the beginning of a new paragraph. Multiple spaces or multiple lines have the same effect as one space or one line. Any number of spaces will not give you more space. How to put more space? That requires some special work that we will see. So, adding some structure used to document class. On the top, we are supposed to say these are different classes we can use. There is a notice that this was the first line of a tech file. Document class always comes in the top. Anything before document class has to be a command. Document class is the first important command that latex should find. First important, non-comment line that PDF latex or latex should find. What are these symbols? And what is this finally? Whatever comes between square brackets between this command, this command we will say takes an argument, report. Whatever comes between the argument and the command, if it comes in square brackets like this, that we will say are optional parameters, optional arguments that you may or may not give. So, what are the optional arguments we gave? We said 12 point. 12 point denotes the size of the font size. 12 point is typically a little larger. For presentations, it might be small, but 12 point means it is relatively large. Typically, 10 point is the default. 10 point is the default, which is already quite readable. Most papers, journal papers, conference papers, they all want 10 point. For purpose of readability, you might want 12 point. For draft, for example, for your own printing and reading, if you want to mark comments in the middle, you want some spaces between them. If you want to do some spelling mistake, spelling correction, then you want these fonts to be larger. A4 paper is some size of the paper. It sets the margins. Draft is some particular mode. These are the various significances of these options. Report finally is the classes. The document class command, you have to give this report as the argument to this particular command. In addition to that argument, we have given these optional arguments. Here, those come between square brackets. So, these are all when we say command. From the context, it should be clear that this is a command not on the terminal. It is not a Unix or Linux command. This is a LaTeC command. That is why they will have its effect when you write it inside the tech file. This is an argument for this LaTeC command. How do you write the argument between square brackets? How do you give optional arguments between square brackets? Sorry, the argument is given in between curly brackets. I think I said square. Argument is given between curly brackets and optional arguments are given between square brackets. Please note square, curly. Mistakes there will cause a problem later. Top matter. Let us add the title. What was the name? Date. So, we will add this into our particular tech file. Then, we will compile whether something changes or not we will see. Let us go back to this. So, this is our file. Notice that we had document class here. We are using something called article. Reports are typically larger. Article is smaller. Then, these are some packages. In case this font is not readable, let me open this again with all black. All syntax is fairly lost by disabling any colors, but I hope this is more readable. For the purpose of readability, I am using this. If you are using VI, then you do not have to do the set term equal to VT 100. Please do not do it for yourself because you can use the advantage of colors. This is the main thing. These are some optional packages which do not come with default, but these are whenever you install latex, these are all always going to be there. What is the significance of this? We will vary a little later today. Here is title. We have set the title author date. All this has come before begin document. Begin document marks the beginning of the document. Whatever is here is also called preamble. Some people call this preamble. This is the entire content. Let me make this little smaller. So, this much is all before the begin document. The document is actually starting here. This is called preamble. One can have longer preamble here. Here is where begin document is. Only after begin document whatever you type will actually come, will come on the PDF file. Whatever is before the begin document, they are important. They are very much important, but that is called preamble. They denote for example, overall settings of the documents. Margins are set here. Any packages you want are set here. New commands. In fact, given the title author information is specified here. Even though they are not going to come on the screen, until they will not come in the PDF file, until you use make title. Make title puts that information on the screen. Then this begin document. So, what we will do? We will just end the document here. Our document has only make title. I am using this within VI editor. If you are using GI edit, if you are using nano, that is up to you. Please use whatever you are most comfortable in and save the file. So, we have just now written the file to glimpse. Now, we will compile it. For compile we had used this. So, it has compiled and come back to the prompt. Always pay attention to this particular fact. I do not recommend using integrated environments only because it does not say explicitly whether you have come back to the prompt or not. After you have become careful that whether you are coming back to the prompt or not, after you are always paying attention, only then you will shift to integrated development for any for latex. Until then please go to this particular policy. Write a file in a text editor. Go to the prompt. Compile it and view the document. You view the PDF file using a document viewer. Please do not use shortcuts until this particular case. Just like we do not teach shortcuts in adding numbers, multiplying as the first thing in school. The first thing we teach is the routine way. Later on after you know the routine way well, then you start using shortcuts. So, please use the routine way here. Then, so now that we have compiled it, let us see what the PDF file looks. No need to compile 2, 2, 3, 3 times the way I am doing. When do you need to compile 2 times that we will see a little later. So, notice that the PDF file has only this much information. How much information? Title, author and date. Notice that we want the title to be larger. We want the author name to be little smaller. We want the date to be even smaller. These things we do not have to worry about now. That is what latex is supposed to do. We are supposed to tell latex what is the title? What size should the title be? That is not for us to worry about. As soon as you choose article class, these things can set default. Of course, you can change this. These things are very much changeable, but the default is what we do not have to worry about. That has been set account to some standards. So, there is no abstract here. Why is there no abstract? Let us go back to our tech file. In our tech file, we put our end document right here. Why do not we comment this and see what happens? So, I put a percent before this make title and I have written, I am writing the file. Let us go back to this. Again I compile. It says no pages of output. Why there is no pages of output? Because after begin document, there is nothing before end document. There is nothing between the begin and end documents. Because of that, there is no page of output. There should be at least something between the two. Then only that is produced in the output file, in the PDF file. Why do not we uncomment this? Now, this particular make title is not receded by a percent symbol. Now, this is not a comment. It is very much going to have its effect. Now, it says output return and it also says one page. How many bytes? Some information provides whether you need it or not. It is providing this information. If you want all this information, it will be there in a log file. If it has come on the screen and you missed it, it is all there in a log file in a little more elaborate way actually. Let us go back to this PDF file. Again, this particular PDF file has come. It was already open using events. Now, the next thing we will do is, let us go back to the slide. Make title inserts the top matter. Add the command make title itself between the begin document and end document. Typically, you want the title to be the top. So, immediately after begin document, you put make title. We had specified the date as June 2010. Remember, if you do not put any date, then today's date is automatically generated. That is also important because you might have multiple versions of PDF files and you want to keep track, which is the latest version. So, there are some questions. We will take some questions back on Aview. The next question is from IMCC Pune. Please ask your question. Okay. Actually, while running this particular PDF latex file, we are getting some error about listings.sdy. And I have gone through the complete .sdy files. It shows that it shows that it is listing. s is not there. So, can you just explain this particular part? So, let me point out. Let us go back to this particular tech file. So, here there is begin document class. There are some packages here. One package was AMS math. One was graphics, color listings. So, its comment is whether the s should be there or not. So, listings, the significance of listing, we will worry later. Why? Because we are first concerned with having some output. My first comment is whether there is a s or not, we will worry a little later. Why? What is the significance of listings? We do not even know that. Then we will start answering whether s is important or not. Hence, if you are getting an error because of this, I suggest you just comment it using a percent symbol. As soon as you see this, then the latex will not even read this particular line. Second important thing is we will say latex, tech as in technology, not latex, not PDF latex. We will say PDF latex, again tech as in technology. So, in case this use package listings is giving you an error, I recommend that you just put a percent symbol while we will take some time and worry about this, because it is not required for what we are saying. Because you have commented it, now this one will give an error. So, I suggest you just delete this. So, whether you delete or you put a comment is the same. So, what I am doing is I have just commented it. Whether the comment is as a first symbol on that line or later does not matter. It should only spaces before it is not a problem. So, either you remove it or delete it. Any of the two is ok. Why did we comment this? Because listings package is what tells what is this LST set command. And we have now commented out use package listings. Hence, I recommend that you also comment this or you delete it. If you delete it, then you will be able to compile and we are now concerned about title author date that part will still work. So, the purpose of what we were discussing was that if you do not put a date, if you do if you comment it out, then date, today's date is automatically generated. How will it know today? It takes from the computer's clock. If your computer clock is wrong time wrong date, then it will show a different date. It will show the date from this computer's clock. So, let us write this and compile again using PDF latex. So, here is again our document. Notice I just put November 13, 2011 that is because on this computer it is 13 November that indeed today is 13 November. So, how did this date change automatically? Because we did not put any date. Are we forced to put a date or today's date? No, you can also go back here to the tech file. We can put MT here slash date curly bracket open, curly bracket close. Argument what is being given as argument? MT nothing is being given as argument that is different from this. You might check both if you want. So, we have saved the file slash date open close curly brackets. Now, we will compile again, then you see the date has not come. If you do not want the date to come, then you have to put slash date curly brackets open close. If you do not put date command at all that is the same as commenting out that line, then today's date will be generated. This is relatively unintuitive that is why I am emphasizing this. Let us go back to this. Let us go back to the slides. Abstract environment. Begin abstract. When we say environment here, you will always remember that abstract is an environment. So, you will use begin abstract and abstract. Where will this begin abstract and abstract come? Wherever you want it to come in the PDF file, in that particular this is its PDF latex will read it sequentially. Let us go to this particular terminal here. First we have make title, then we have put this end document. Why do not we comment it out? Because you comment it out latex will read further and we will see begin abstract. So, PDF latex when you do it will compile line by line it will go sequentially. First it has seen make title it will put the title on the top of the PDF file on the beginning on the first page. Then there is page in that particular there is space there is further space inside that particular first page. So, begin abstract end abstract will also come there. Then there is this end document. So, it will not read further it will not go further say there is some section all the section is there after the end document. It is going line by line first make title has come then begin abstract. Whatever you type between begin and end abstract will come as the abstract. This is an environment. What is the purpose of having a separate environment? First of all it will put the title it will put the word abstract what what is the effect we will see very soon. So, begin a glimpse at sci-fi has come posi has come date has not come because we put those empty argument to the date command abstract has come in little bold and small font bold and small font. This particular font of course looks smaller than this we will very soon see that it is smaller than the rest of the it is smaller than 12 point because it is supposed to be abstract it is put in smaller font. This is abstract has come in the center. Did you put the abstract word? No begin abstract end abstract environment will tell that one abstract word should come like this in the middle. Moreover it should be bold.