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Compiler Design PYQs for GATE CS

GATE CS Compiler Design: 6 chapters, 43 previous year questions (100% of Compiler Design), 25 practice questions and one solved question from each chapter.

A question from this chapter

Question 1

2026 Slot Set2 PYQ

Level 3: Exam Standard

A lexical analyzer uses the following token definitions • l e tt er \to [A - Z a - z] • d i g i t \to [0 - 9] • i d \to l e tt er (l e tt er ∣ d i g i t)^{*} • n u mb er \to d i g i t^{+} • w s \to (b l ank ∣ t ab ∣ n e w l in e)^{+} For the string given below, x 123 mm 78 y 7 z z z 514 A 8 H A aY cD the number of tokens (excluding w s) that will be produced by the lexical analyzer is __________. (answer in integer)

Question 2

2026 Slot Set1 PYQ

Which of the following statements is/are true?

Question 3

2026 Slot Set2 PYQ

Consider the canonical L R (0) parsing of the grammar below using terminals {a, b, c} and non-terminals {A, B, C, S} with S as the start symbol. S \to A C B A \to a A ∣ ϵ C \to c C ∣ ϵ B \to b B ∣ b Which one of the following options gives the number of shift-reduce conflicts that will occur in the L R (0) ACTION table?

Question 4

2026 Slot Set1 PYQ

Consider the following two syntax-directed definitions SDD1 and SDD2 for type declarations. SDD1 SDD2 Grammar (G1) Semantic Rules Grammar (G2) Semantic Rules D \to T V D . t y p e = T . t y p e V . t y p e = T . t y p e D \to D_{1} i d D . t y p e = D_{1} . t y p e p u t (i d . e n t r y, D_{1} . t y p e) T \to in t T . t y p e = in t D \to T i d D . t y p e = T . t y p e p u t (i d . e n t r y, T . t y p e) T \to f l o a t T . t y p e = f l o a t T \to in t T . t y p e = in t V \to V_{1} i d V_{1} . t y p e = V . t y p e p u t (i d . e n t r y, V . t y p e) T \to f l o a t T . t y p e = f l o a t V \to i d p u t (i d . e n t r y, V . t y p e) D is the start symbol, and in t, f l o a t and i d are the three terminals. The non-terminal V_{1} is the same as V and the non-terminal D_{1} is the same as D . Here, the subscript is used to differentiate the grammar symbols on the two sides of a production. The function p u t updates the symbol table with the type information for an identifier. Let P and Q be the languages specified by grammars G1 and G2, respectively. Which of the following statements is/are true?

Question 5

2023 PYQ

Consider the following program: int main() {f1(); f2(2); f3(); return(0);} int f1() {return(1);} int f2(int X) {f3(); if (X==1) return f1(); else return (X*f2(X-1));} int f3() {return(5);} Which one of the following options represents the activation tree corresponding to the main function?

Question 6

2026 Slot Set2 PYQ

Consider the control flow graph given below. ENTRY B1 a = b + c B2 d = a + e B3 e = a + f B4 g = d + e EXIT Which one of the following options is the set of live variables at the exit point of each basic block?

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Compiler Design PYQs for GATE CS

GATE CS Compiler Design: 6 chapters, 43 previous year questions (100% of Compiler Design), 25 practice questions and one solved question from each chapter.

About Compiler Design Previous Year Questions (PYQs)

43 previous year questions from Compiler Design in GATE CS, grouped by chapter with the exam year, answer key and step-by-step solution for each.

Compiler Design Weightage in GATE CS

Compiler Design accounts for 43 of 43 Compiler Design previous year questions in our bank (100%), about 4.3 per paper across 10 papers.

Compiler Design Chapter Matrix

Chapter	Topics	PYQs	Share of unit PYQs	Practice questions
Compiler Phases, Lexical Analysis and Semantic Processing	Compiler Phases, Front-End, Back-End and Symbol Tables, Lexical Tokens, Regular Expressions and Finite Automata, Semantic Analysis and Syntax-Directed Type Checking, Lexical, Syntax and Semantic Error Classification	9	21%	25
Top-Down and Predictive Parsing	FIRST and FOLLOW Set Computation, LL(1) Grammar Conditions and Predictive Parsing, LL(1) Parsing Table Construction	6	14%	0
Bottom-Up and LR Parsing	Bottom-Up Parser Types and LR Grammar Classes, Operator Precedence and Shift-Reduce Parsing, LR Item Closure and GOTO Computation, LR Parsing Conflicts and Grammar Ambiguity	8	19%	0
Syntax-Directed Translation and Intermediate Representations	Backpatching and Control-Flow Code Generation, Syntax-Directed Definitions and Attribute Evaluation, Intermediate Representations and Triple Code	9	21%	0
Runtime Environments and Procedure Calls	Activation Trees and Procedure Call Sequences	2	5%	0
Basic Blocks, Data-Flow Analysis and Code Optimization	Basic Blocks and Control-Flow Graph Construction, Live Variables and Data-Flow Analysis, DAG Optimization, Common Subexpressions and Available Expressions	9	21%	0

One Solved Question from Each Compiler Design Chapter

Question 1 · Compiler Phases, Lexical Analysis and Semantic Processing · 2026_Set2 NAT

A lexical analyzer uses the following token definitions

•

l e tt er \to [A - Z a - z]

•

d i g i t \to [0 - 9]

•

i d \to l e tt er (l e tt er ∣ d i g i t)^{*}

•

n u mb er \to d i g i t^{+}

•

w s \to (b l ank ∣ t ab ∣ n e w l in e)^{+}

For the string given below,

x 123 mm 78 y 7 z z z 514 A 8 H A aY cD

the number of tokens (excluding

w s

) that will be produced by the lexical analyzer is __________. (answer in integer)

Correct Answer:

Step-by-Step Solution

Key idea: Apply the maximal munch rule (longest match) to tokenize the input string based on the given regular expressions.

Step 1: The input string is separated by whitespace. We process each space-separated chunk.

Step 2: x1 starts with a letter and is followed by a digit. Matches id. (1 token)

Step 3: 23mm starts with digits. The longest match for number is 23. The remaining mm matches id. (2 tokens)

Step 4: 78 matches number. (1 token)

Step 5: y matches id. (1 token)

Step 6: 7z starts with a digit. 7 matches number. z matches id. (2 tokens)

Step 7: zz5 starts with a letter, followed by letters/digits. Matches id. (1 token)

Step 8: 14A starts with digits. 14 matches number. A matches id. (2 tokens)

Step 9: 8H starts with a digit. 8 matches number. H matches id. (2 tokens)

Step 10: AaYcD starts with a letter, followed by letters. Matches id. (1 token)

Step 11: Sum the tokens: 1 + 2 + 1 + 1 + 2 + 1 + 2 + 2 + 1 = 13.

Answer: 13

Question 2 · Top-Down and Predictive Parsing · 2026_Set1 MSQ

Which of the following statements is/are true?

A.
LL(1) parser uses backtracking
B.
For a grammar to be LL(1), it must be left-recursive
C.
For a grammar to be LL(1), it must be left-factored
D.
The LL(1) parsers are more powerful than the SLR parsers

Question 3 · Bottom-Up and LR Parsing · 2026_Set2 MCQ

Consider the canonical

L R (0)

parsing of the grammar below using terminals

{a, b, c}

and non-terminals

{A, B, C, S}

with

S

as the start symbol.

S \to A C B

A \to a A ∣ ϵ

C \to c C ∣ ϵ

B \to b B ∣ b

Which one of the following options gives the number of shift-reduce conflicts that will occur in the

L R (0)

ACTION table?

A.
2
B.
3
C.
4
D.
5

Question 4 · Syntax-Directed Translation and Intermediate Representations · 2026_Set1 MSQ

Consider the following two syntax-directed definitions SDD1 and SDD2 for type declarations.

SDD1		SDD2
Grammar (G1)	Semantic Rules	Grammar (G2)	Semantic Rules
$D \to T V$	$D . t y p e = T . t y p e$ $V . t y p e = T . t y p e$	$D \to D_{1} i d$	$D . t y p e = D_{1} . t y p e$ $p u t (i d . e n t r y, D_{1} . t y p e)$
$T \to in t$	$T . t y p e = in t$	$D \to T i d$	$D . t y p e = T . t y p e$ $p u t (i d . e n t r y, T . t y p e)$
$T \to f l o a t$	$T . t y p e = f l o a t$	$T \to in t$	$T . t y p e = in t$
$V \to V_{1} i d$	$V_{1} . t y p e = V . t y p e$ $p u t (i d . e n t r y, V . t y p e)$	$T \to f l o a t$	$T . t y p e = f l o a t$
$V \to i d$	$p u t (i d . e n t r y, V . t y p e)$

D

is the start symbol, and

in t

f l o a t

and

i d

are the three terminals. The non-terminal

V_{1}

is the same as

V

and the non-terminal

D_{1}

is the same as

D

. Here, the subscript is used to differentiate the grammar symbols on the two sides of a production. The function

p u t

updates the symbol table with the type information for an identifier.

Let P and Q be the languages specified by grammars G1 and G2, respectively.

Which of the following statements is/are true?

A.
The languages P and Q are the same
B.
SDD2 is S-attributed and contains only synthesized attributes
C.
SDD1 is L-attributed and contains only inherited attributes
D.
The specifications of SDD1 and SDD2 are such that the same entries get added to the symbol table

Question 5 · Runtime Environments and Procedure Calls · 2023 MCQ

Consider the following program:

int main()
{
   f1();
   f2(2);
   f3();
   return(0);
}

int f1()
{
   return(1);
}

int f2(int X)
{
   f3();
   if (X==1)
      return f1();
   else
      return (X*f2(X-1));
}

int f3()
{
   return(5);
}

Which one of the following options represents the activation tree corresponding to the main function?

Question 6 · Basic Blocks, Data-Flow Analysis and Code Optimization · 2026_Set2 MCQ

Consider the control flow graph given below.
Which one of the following options is the set of live variables at the exit point of each basic block?

A.
B1:{a, b, c, e, f}, B2:{d, e}, B3:{b, c, e, f}, B4: $\emptyset$
B.
B1: $\emptyset$ , B2:{d, e}, B3:{a, c, f}, B4: $\emptyset$
C.
B1:{a, b, c, e, f}, B2:{d, e}, B3:{c, e, f}, B4: $\emptyset$
D.
B1: $\emptyset$ , B2:{d, e, f}, B3:{a, b, c, e, f}, B4: $\emptyset$

A question from this chapter

Login to view the complete previous-year questions and solutions

Personalised first. High quality throughout.

Built around you, not around a syllabus PDF

Revision that hits your weak spots

Questions calibrated to the real exam

Notes written for recall, not for volume

One place for everything

Honest progress

Unlock the whole course

Compiler Design PYQs for GATE CS

About Compiler Design Previous Year Questions (PYQs)

Compiler Design Weightage in GATE CS

Compiler Design Chapter Matrix

More from Compiler Design

One Solved Question from Each Compiler Design Chapter

Step-by-Step Solution