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Syntax-Directed Translation and Intermediate Representations PYQs for GATE CS

Solve 9+ Syntax-Directed Translation and Intermediate Representations previous year questions for GATE CS with answers and detailed solutions. Free sample que

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Question 1

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 2

2025 Slot Set2 PYQ

Consider the following statements about the use of backpatching in a compiler for intermediate code generation: (I) Backpatching can be used to generate code for Boolean expression in one pass. (II) Backpatching can be used to generate code for flow-of-control statements in one pass. Which ONE of the following options is CORRECT?

Question 3

2025 Slot Set2 PYQ

Given the following syntax directed translation rules: Rule 1: R \to A B {B . i = R . i - 1; A . i = B . i; R . i = A . i + 1;} Rule 2: P \to C D {P . i = C . i + D . i; D . i = C . i + 2;} Rule 3: Q \to E F {Q . i = E . i + F . i;} Which ONE is the CORRECT option among the following?

Question 4

2024 Slot Set2 PYQ

Consider the following expression: x [i] = (p + r) * - s [i] + u / w . The following sequence shows the list of triples representing the given expression, with entries missing for triples (1), (3), and (6). (0) + p r (1) (2) uminus (1) (3) (4) / u w (5) + (3) (4) (6) (7) = (6) (5) Which one of the following options fills in the missing entries CORRECTLY?

Question 5

2024 Slot Set2 PYQ

Which of the following statements is/are FALSE?

Question 6

2024 Slot Set1 PYQ

Consider the following syntax-directed definition (SDD). S \to D H T U {S . v a l = D . v a l + H . v a l + T . v a l + U . v a l;} D \to "M" D_{1} {D . v a l = 5 + D_{1} . v a l;} D \to ϵ {D . v a l = - 5;} H \to "L" H_{1} {H . v a l = 5 * 10 + H_{1} . v a l;} H \to ϵ {H . v a l = - 10;} T \to "C" T_{1} {T . v a l = 5 * 100 + T_{1} . v a l;} T \to ϵ {T . v a l = - 5;} U \to "K" {U . v a l = 5;} Given "MMLK" as the input, which one of the following options is the CORRECT value computed by the SDD (in the attribute S . v a l)?

Question 7

2023 PYQ

Consider the syntax directed translation given by the following grammar and semantic rules. Here N, I, F and B are non-terminals. N is the starting non-terminal, and #, 0 and 1 are lexical tokens corresponding to input letters “#”, “0” and “1”, respectively. X . v a l denotes the synthesized attribute (a numeric value) associated with a non-terminal X . I_{1} and F_{1} denote occurrences of I and F on the right hand side of a production, respectively. For the tokens 0 and 1, 0. v a l = 0 and 1. v a l = 1 . N \to I # F N . v a l = I . v a l + F . v a l \I \to I_{1} B I . v a l = (2 I_{1} . v a l) + B . v a l \I \to B I . v a l = B . v a l \F \to B F_{1} F . v a l = \frac{1}{2} (B . v a l + F_{1} . v a l) \F \to B F . v a l = \frac{1}{2} B . v a l \B \to 0 B . v a l = 0. v a l \B \to 1 B . v a l = 1. v a l The value computed by the translation scheme for the input string 10#011 is __________. (Rounded off to three decimal places)

Question 8

2022 PYQ

Consider the following grammar along with translation rules. S S T T R \to S_{1} # T \to T \to T_{1} % R \to R \to i d {S_{. v a l} = S_{1. v a l} * T_{. v a l}} {S_{. v a l} = T_{. v a l}} {T_{. v a l} = T_{1. v a l} \div R_{. v a l}} {T_{. v a l} = R_{. v a l}} {R_{. v a l} = i d_{. v a l}} Here # and % are operators and i d is a token that represents an integer and i d_{. v a l} represents the corresponding integer value. The set of non-terminals is {S, T, R, P} and a subscripted non-terminal indicates an instance of the non-terminal. Using this translation scheme, the computed value of S_{. v a l} for root of the parse tree for the expression 20#10%5#8%2%2 is_____________.

Question 9

2021 Slot Set2 PYQ

In the context of compilers, which of the following is/are NOT an intermediate representation of the source program?

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Syntax-Directed Translation and Intermediate Representations PYQs for GATE CS

Solve 9+ Syntax-Directed Translation and Intermediate Representations previous year questions for GATE CS with answers and detailed solutions. Free sample questions below.

Chapter Roadmap: Syntax-Directed Translation and IR

Chapter Roadmap

Your visual journey through the compiler's middle-end.

Step 1: Syntax-Directed Definitions

The Heavyweight (High Exam Yield)

Attaching semantic rules to grammar. Inherited vs. Synthesized attributes. Dependency graphs.

Step 2: Backpatching & Control Flow

The Current Topic (Core Logic)

Translating boolean logic and control structures (if, while) into Three-Address Code in a single pass.

Step 3: Intermediate Representations

The Formats (Direct Applications)

Quadruples, Triples, and Indirect Triples. How the code is actually stored in memory.

What you will master: Tracing how a high-level while loop is parsed and converted into low-level jump instructions without a second pass.

The Forward Reference Problem in One-Pass Compilation

The Forward Reference Problem

When generating code for control structures like if or while, the compiler faces a dilemma in a single pass:

if (x < y) {
// ... 50 lines of code ...
}
// Target Line Unknown!

The compiler evaluates x < y and needs to emit a jump for the false condition. But the target address (after the 50 lines) hasn't been generated yet.

Two-Pass Compilation

Pass 1 records block ends. Pass 2 generates code. Simple but slow and memory-heavy.

Backpatching (One-Pass)

Emit goto _ with a blank target. Record the location. "Patch" the address when the target is finally reached.

Syntax-Directed Translation and Intermediate Representations: Solved Questions with Step-by-Step Explanations (9 Problems)

Question 1 · Compiler Design · 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 2 · Compiler Design · 2025_Set2 MCQ

Consider the following statements about the use of backpatching in a compiler for intermediate code generation:

(I) Backpatching can be used to generate code for Boolean expression in one pass.
(II) Backpatching can be used to generate code for flow-of-control statements in one pass.

Which ONE of the following options is CORRECT?

A.
Only (I) is correct.
B.
Only (II) is correct.
C.
Both (I) and (II) are correct.
D.
Neither (I) nor (II) is correct.

Question 3 · Compiler Design · 2025_Set2 MCQ

Given the following syntax directed translation rules:

Rule 1:

R \to A B {B . i = R . i - 1; A . i = B . i; R . i = A . i + 1;}

Rule 2:

P \to C D {P . i = C . i + D . i; D . i = C . i + 2;}

Rule 3:

Q \to E F {Q . i = E . i + F . i;}

Which ONE is the CORRECT option among the following?

A.
Rule 1 is S-attributed and L-attributed; Rule 2 is S-attributed and not L-attributed; Rule 3 is neither S-attributed nor L-attributed
B.
Rule 1 is neither S-attributed nor L-attributed; Rule 2 is S-attributed and L-attributed; Rule 3 is S-attributed and L-attributed
C.
Rule 1 is neither S-attributed nor L-attributed; Rule 2 is not S-attributed and is L-attributed; Rule 3 is S-attributed and L-attributed
D.
Rule 1 is S-attributed and not L-attributed; Rule 2 is not S-attributed and is L-attributed; Rule 3 is S-attributed and L-attributed

Question 4 · Compiler Design · 2024_Set2 MCQ

Consider the following expression:

x [i] = (p + r) * - s [i] + u / w

. The following sequence shows the list of triples representing the given expression, with entries missing for triples (1), (3), and (6).

Which one of the following options fills in the missing entries CORRECTLY?

A.
$(1) = [] s i (3) * (0) (2) (6) [] = x i$
B.
$(1) [] = s i (3) - (0) (2) (6) = [] x (5)$
C.
$(1) = [] s i (3) * (0) (2) (6) [] = x (5)$
D.
$(1) [] = s i (3) - (0) (2) (6) = [] x i$

Question 5 · Compiler Design · 2024_Set2 MSQ

Which of the following statements is/are FALSE?

A.
An attribute grammar is a syntax-directed definition (SDD) in which the functions in the semantic rules have no side effects
B.
The attributes in a L-attributed definition cannot always be evaluated in a depth-first order
C.
Synthesized attributes can be evaluated by a bottom-up parser as the input is parsed
D.
All L-attributed definitions based on LR(1) grammar can be evaluated using a bottom-up parsing strategy

Question 6 · Compiler Design · 2024_Set1 MCQ

Consider the following syntax-directed definition (SDD).

S \to D H T U

{S . v a l = D . v a l + H . v a l + T . v a l + U . v a l;}

D \to "M" D_{1}

{D . v a l = 5 + D_{1} . v a l;}

D \to ϵ

{D . v a l = - 5;}

H \to "L" H_{1}

{H . v a l = 5 * 10 + H_{1} . v a l;}

H \to ϵ

{H . v a l = - 10;}

T \to "C" T_{1}

{T . v a l = 5 * 100 + T_{1} . v a l;}

T \to ϵ

{T . v a l = - 5;}

U \to "K"

{U . v a l = 5;}

Given "MMLK" as the input, which one of the following options is the CORRECT value computed by the SDD (in the attribute

S . v a l

A.
$45$
B.
$50$
C.
$55$
D.
$65$

Question 7 · Compiler Design · 2023 NAT

Consider the syntax directed translation given by the following grammar and semantic rules. Here

N

I

F

and

B

are non-terminals.

N

is the starting non-terminal, and #, 0 and 1 are lexical tokens corresponding to input letters “#”, “0” and “1”, respectively.

X . v a l

denotes the synthesized attribute (a numeric value) associated with a non-terminal

X

I_{1}

and

F_{1}

denote occurrences of

I

and

F

on the right hand side of a production, respectively. For the tokens 0 and 1,

0. v a l = 0

and

1. v a l = 1

N \to I # F N . v a l = I . v a l + F . v a l \I \to I_{1} B I . v a l = (2 I_{1} . v a l) + B . v a l \I \to B I . v a l = B . v a l \F \to B F_{1} F . v a l = \frac{1}{2} (B . v a l + F_{1} . v a l) \F \to B F . v a l = \frac{1}{2} B . v a l \B \to 0 B . v a l = 0. v a l \B \to 1 B . v a l = 1. v a l

The value computed by the translation scheme for the input string

10#011

is __________. (Rounded off to three decimal places)

Question 8 · Compiler Design · 2022 NAT

Consider the following grammar along with translation rules.

S S T T R \to S_{1} # T \to T \to T_{1} % R \to R \to i d {S_{. v a l} = S_{1. v a l} * T_{. v a l}} {S_{. v a l} = T_{. v a l}} {T_{. v a l} = T_{1. v a l} \div R_{. v a l}} {T_{. v a l} = R_{. v a l}} {R_{. v a l} = i d_{. v a l}}

Here # and % are operators and

i d

is a token that represents an integer and

i d_{. v a l}

represents the corresponding integer value. The set of non-terminals is

{S, T, R, P}

and a subscripted non-terminal indicates an instance of the non-terminal.

Using this translation scheme, the computed value of

S_{. v a l}

for root of the parse tree for the expression

20#10%5#8%2%2

is_____________.

Question 9 · Compiler Design · 2021_Set2 MSQ

In the context of compilers, which of the following is/are NOT an intermediate representation of the source program?

A.
Three address code
B.
Abstract Syntax Tree (AST)
C.
Control Flow Graph (CFG)
D.
Symbol table

Try a question

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

Syntax-Directed Translation and Intermediate Representations PYQs for GATE CS

Chapter Roadmap: Syntax-Directed Translation and IR

Chapter Roadmap

The Forward Reference Problem in One-Pass Compilation

The Forward Reference Problem

Two-Pass Compilation

Backpatching (One-Pass)

Syntax-Directed Translation and Intermediate Representations: Solved Questions with Step-by-Step Explanations (9 Problems)

More previous year questions (pyqs) in this unit