🔥 BCS613C Module 3 Compiler Design | Overview + Important Topics + MQP & PYQ Answers 💯 #vtu #bcs316c

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[00:00:00]So, hi, hello, everyone. Welcome back to the our YouTube channel. So far, we have covered the module one and module two of this compiler design subject. The subject code BCS613C.

[00:00:12]Important concepts and overview of the each module. In this video, we are going to discussing about the module three important concepts and the model question paper previous year question paper question answers we are going to solving.

[00:00:25]You know, only one two days left for the exam. So, for that reason, I am focusing on you to practice these questions because here I have listed only important concepts. I have not added the theory, I know, other than all syllabus.

[00:00:42]And as comparatively all five modules, this module three have a very small topics. And you know, you can you have already seen in the syllabus copy that is it is having a two chapters, top down parsing and bottom bottom up parsing.

[00:01:01]Based on that, here they will ask ask to construct the LL1 grammar uh and SR parsing grammar. Here, most of the questions are comes under from this LL1 and SR parsing grammar table itself.

[00:01:17]Okay? So, what I am planning that here I am going to discussing about the theory content and you know, theory content and important uh concepts I will explain. And whatever the constructions and expression grammars are there, I will try to solve one by one because if you observe in the model question paper and previous year question paper, see, here they will give you one grammar, you need to construct the LL1 grammar. And again, here it is also LL1 grammar design and SR SR parsing table they will ask in the module three.

[00:01:55]Other than that, they will ask like uh explain recursive descent parsing table like that. Let's see the In this video, I will try to explain the theory content theory questions.

[00:02:08]Um, then I will solve one by one from this model questions, okay? So, here again, if you see the previous year question paper, there there there are all all four four questions are based on the grammar itself. So, yeah, here and also um there are some standard expressions are there. You you If you are practicing with that, there might be a possible You know, there might be a chance of uh coming the questions in the upcoming exam. Let's start one by one. So, first uh four questions are all about the construction of a grammar.

[00:02:45]Uh that is a LL of one first and follow, then comes a SR parsing table.

[00:02:53]All these are there in the first four questions. I'm not explaining here because if I start explaining orally just with this content, you might feel a confusion. So, that's why to avoid that confusion, I'm just focusing on the theory content here. So, first four, as I told you know, first four all about the grammar question answer is there.

[00:03:15]I will try one by one, okay? I will solve manually one by one. Uh in this video, let's see the important theory content. The first question is recursive descent parsing. See, the model question paper, they have asked it.

[00:03:29]Explain the recursive descent parsing with an example. So, you need to You need to answer for this question.

[00:03:36]The recursive parsing table, it is a top-down parsing technique, okay? It is a top-down parsing technique.

[00:03:44]In a in which a set of recursive procedures is used to process the input data. So, there there will be already solved the you know expression will we will get to request you that you know to get back into the input string we need we will follow this recursion discount parsing.

[00:04:04]In this case, you every time we solve the one grammar, we will solve into the solution grammar, right? But here uh uh here what what what happens again uh directly input I I I directly solved the expression will be So, you need to extract the solved expression with the input string. What kind of input string it will get? Every time with the input string we need to solve the expression. It is a reverse of the that topic, okay? So, let's take an example. E tends to E T E' and E' tends to + T E' and empty. T tends to ID is there. The input string is ID ID plus. So, for this you need the recursion procedure is the following program. Short program is there. Okay.

[00:04:50]So, next the question is explain shift reduce parsing technique is there. So, uh yeah.

[00:04:59]Uh explain a shift reduce parsing. Here it is a bottom-up parsing. So, that the recursive descent parsing is a top-down parsing whereas SR parsing is a bottom-up parsing technique used in the compiler design to analyze the construct syntax tree for to construct a syntax tree for a programming languages.

[00:05:19]To construct the syntax for the programming language, we are using this SR parsing. So, SR parsing and recursive descent parsing, those are all these both are comes under in a uh uh you know, top-down parsing and bottom-up parsing techniques. Then, yeah, this uh shift reduce parsing have a uh few parameters.

[00:05:39]First one is shift. So, shift is nothing but it is a move the next input symbol on the generally like a generally shift is nothing but a shifting, right?

[00:05:49]Moving forward. That is what it does.

[00:05:52]Reduce Reduce is nothing but a replacing a sequence of a program of a grammar symbol on the stack. So, replace a sequence of a grammar symbol on the stack. If you have if that one value E tends to something is there and that something value if you have, so you can just reduce it into the E value. So, that is what it does. Next, a handle. The handle substring that matches the right-hand side of the production and can replace by the left-hand side. Next comes the dollar. It is a bottom bottom of the stack and the end of the input string. It will demonstrate at a empty or end of the string.

[00:06:32]So, dollar symbol. Again, example is there for the SR parsing. Next comes the Write a procedure to compute the first and follow of the given grammar. Yeah, this question is also there. Where Yeah, here it is. Write a procedure to compute the first and follow.

[00:06:48]Um In this third module, it is a important concept because if because based on this first and follow uh follow grammar only, we will solve the LL1 LL1 and uh another topic. So, you must have to know about the how to do the compute the first and follow. So, here some procedures are there. First, if X is a terminal, take of X, that is equals to X. So, X is having a terminal. Then, you directly directly first of X is equals to X, you need to write the X itself. If X is having a empty, then add a empty to the that string, that production. So, first of X is a same. Then, if X tends to Y1 Y2 YN. Here, Y1 Y2 are the if if these are non-terminal, you will directly enter directly enter the that Y1 itself. Or if if it is having a terminal, you need to take again first of that uh Sorry, if it is having a non-terminal, you directly you have to take again first of that non-terminal value. If it is a terminal, you directly goes to write the terminal.

[00:08:05]So, just follow these procedure steps, uh you will understand. Next come when you start to solve this first and follow procedure problems, then you will understand the steps. Then comes the follow as like a first only here we are going to uh see the follow of the value. If the value is there let's take it this is an X. So, to find the follow of X, whatever there in front of the X, you need to you need to write in the curly bracket. That is what first only is a place the dollar in a follow. So, initially you need to mention the dollar as a in in starting symbol. Uh then then the initial one. Then for for each production A tends to alpha B beta, add a first of beta. See, uh first of B is a uh first First of follow of A is a nothing but a Here add a first of B beta except a null is there to follow a B. To find the follow of B, you have a small terminal you you need to write like that. So, again four steps is there.

[00:09:13]Uh if you once you start to finding a first and follow, you will understand the these steps, okay?

[00:09:19]Next comes the handle pruning and in a bottom-up parsing. This is also there.

[00:09:23]Uh yeah, ex- see in the model question paper itself. Explain handle pruning with the example with an example.

[00:09:31]So, here handle pruning example you need to explain by taking one example. Here I have taken taken ID plus ID string. For string, you need to uh um draw this table with the with this grammar, okay? So, yeah. Here again, regarding about the handle pruning description is there. So, it is essential the process of constructing the right most derivation in a reverse.

[00:09:59]Each reduction steps corresponding to the pruning a handle from a sentential form a uh and from until only the start symbol remains. And again, the grammar is it is there. Next, finally, the next question from the previous year question paper. This is also so grammar grammar.

[00:10:20]Yeah, here. Write a recursive descent for the following grammar. They have already solved the grammar they have given. You need to write the descent.

[00:10:28]So, for that Yeah, here it is. Write a recursive descent for the following grammar. This For this grammar, you need to write the descent. Here, it is the description, then the with the example, you need to explain. That's it.

[00:10:43]That's it all about the um theory content. I will explain each uh starting four questions, whatever the uh LL1 SR parsing they have asked no to solve to construct. I will I will explain with the each one by one.

[00:11:00]And also, I'm thinking that in the module four, it is also having a almost a 90% uh questions are like this only.

[00:11:08]Uh constructing a grammar, solving the expression grammars, and all those things.

[00:11:13]Uh that's why I will first cover the theory content so that you people are you know you know just understanding the concept will be able to write in your exam. After that, we'll start to solve the one by one.

[00:11:27]Yeah.

[00:11:30]Uh fourth module will also do like that only. So, fifth module it is having almost all theory content. Uh, I will push that uh, first after the fourth module then third this third and fourth module grammars one by one. Let's see, okay?

[00:11:46]Yes, that's it all about this third module, guys. Hope you people are understand. If you have any queries, just let me know in the comment box.

[00:11:54]Uh, thank you.