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Top-Down and Predictive Parsing PYQs for GATE CS

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Question 1

2026 Slot Set1 PYQ

Which of the following statements is/are true?

Question 2

2025 Slot Set2 PYQ

Consider two grammars G_{1} and G_{2} with the production rules given below: G_{1} : S \to if E then S ∣ if E then S else S ∣ a E \to b G_{2} : S \to if E then S ∣ M M \to if E then M else S ∣ c E \to b where if, then, else, a, b, c are the terminals. Which of the following option(s) is/are CORRECT?

Question 3

2025 Slot Set1 PYQ

Which of the following statement(s) is/are <b>TRUE</b> while computing First and Follow during top down parsing by a compiler?

Question 4

2024 Slot Set2 PYQ

Consider the following context-free grammar where the start symbol is S and the set of terminals is {a, b, c, d} . S A B \to A a A b ∣ B b B a \to c S ∣ ϵ \to d S ∣ ϵ The following is a partially-filled LL(1) parsing table. a b c d $ S S \to AaAb S \to BbBa (1) (2) A A \to ε (3) A \to cS B (4) B \to ε B \to dS Which one of the following options represents the CORRECT combination for the numbered cells in the parsing table? Note: In the options, “blank” denotes that the corresponding cell is empty.

Question 5

2024 Slot Set1 PYQ

Consider the following grammar G, with S as the start symbol. The grammar G has three incomplete productions denoted by (1), (2), and (3). S \to d a T ∣ (1) T \to a S ∣ b T ∣ (2) R \to (3) ∣ ϵ The set of terminals is {a, b, c, d, f} . The FIRST and FOLLOW sets of the different non-terminals are as follows. FIRST (S) = {c, d, f}, FIRST (T) = {a, b, ϵ}, FIRST (R) = {c, ϵ} FOLLOW (S) = FOLLOW (T) = {c, f, $}, FOLLOW (R) = {f} Which one of the following options CORRECTLY fills in the incomplete productions?

Question 6

2021 Slot Set1 PYQ

Consider the following context-free grammar where the set of terminals is {a, b, c, d, f} . S T R \to d a T ∣ R f \to a S ∣ ba T ∣ ϵ \to c a T R ∣ ϵ The following is a partially-filled LL(1) parsing table. a b c d f $ S ① S \to d a T ② T T \to a S T \to ba T ③ T \to ϵ ④ R R \to c a T R R \to ϵ Which one of the following choices represents the correct combination for the numbered cells in the parsing table (“blank” denotes that the corresponding cell is empty)?

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Top-Down and Predictive Parsing PYQs for GATE CS

Solve 6+ Top-Down and Predictive Parsing previous year questions for GATE CS with answers and detailed solutions. Free sample questions below.

Chapter Roadmap: Top-Down and Predictive Parsing

Chapter · Top-Down and Predictive Parsing

Three topics, one engine

From "what can start a string" to "which table cell to fill".

FIRST and FOLLOW Set Computation

This topic · moderate weight · 2 PYQs in this course

Build the two foundational sets that make predictive parsing possible. By the end you will compute FIRST and FOLLOW for any CFG by hand.

LL(1) Grammar Conditions and Predictive Parsing

Moderate weight · 2 PYQs in this course

Use FIRST and FOLLOW to decide whether a grammar is LL(1). Master the disjointness condition that removes ambiguity in top-down choices.

LL(1) Parsing Table Construction

Moderate weight · 2 PYQs in this course

Turn the disjointness condition into a concrete table. Fill entries, detect conflicts, and read off parse steps.

By the end of this chapter you will

Compute FIRST and FOLLOW sets for any CFG in under two minutes.
Decide in one glance whether a grammar is LL(1) or not.
Build the full LL(1) parsing table and trace a derivation.

What are FIRST and FOLLOW, and why do they exist?

A top-down parser expands non-terminals one at a time. At each step it must pick a production. To pick correctly while reading the input only once, it needs two pieces of information about every non-terminal $A$ :

FIRST of $A$

The set of terminals that can appear at the very beginning of a string derived from $A$ .

FOLLOW of $A$

The set of terminals that can appear immediately to the right of $A$ in some sentential form.

Together they answer the parser's only real question:

"Given that I am about to expand

A

, and the next input token is

a

, which production of

A

should I use?"

If the grammar is well-behaved (LL(1)), the answer is unique. Computing FIRST and FOLLOW is the first step toward checking that, and toward building the parsing table.

Top-Down and Predictive Parsing: Solved Questions with Step-by-Step Explanations (6 Problems)

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

Consider two grammars

G_{1}

and

G_{2}

with the production rules given below:

G_{1} : S \to if E then S ∣ if E then S else S ∣ a

E \to b

G_{2} : S \to if E then S ∣ M

M \to if E then M else S ∣ c

E \to b

where

if, then, else, a, b, c

are the terminals.

Which of the following option(s) is/are CORRECT?

A.
$G_{1}$ is not $LL (1)$ and $G_{2}$ is $LL (1)$ .
B.
$G_{1}$ is $LL (1)$ and $G_{2}$ is not $LL (1)$ .
C.
$G_{1}$ and $G_{2}$ are not $LL (1)$ .
D.
$G_{1}$ and $G_{2}$ are ambiguous.

Question 3 · Compiler Design · 2025_Set1 MSQ

Which of the following statement(s) is/are <b>TRUE</b> while computing First and Follow during top down parsing by a compiler?

A.
For a production $A \to ϵ$ , $ϵ$ will be added to $F i r s t (A)$ .
B.
If there is any input right end marker, it will be added to $F i r s t (S)$ , where $S$ is the start symbol.
C.
For a production $A \to ϵ$ , $ϵ$ will be added to $F o l l o w (A)$ .
D.
If there is any input right end marker, it will be added to $F o l l o w (S)$ , where $S$ is the start symbol.

Question 4 · Compiler Design · 2024_Set2 MCQ

Consider the following context-free grammar where the start symbol is

S

and the set of terminals is

{a, b, c, d}

S A B \to A a A b ∣ B b B a \to c S ∣ ϵ \to d S ∣ ϵ

The following is a partially-filled LL(1) parsing table.

Which one of the following options represents the CORRECT combination for the numbered cells in the parsing table?

Note: In the options, “blank” denotes that the corresponding cell is empty.

A.
$(1) S \to A a A b (2) S \to B b B a (3) A \to ϵ (4) B \to ϵ$
B.
$(1) S \to B b B a (2) S \to A a A b (3) A \to ϵ (4) B \to ϵ$
C.
$(1) S \to A a A b (2) S \to B b B a (3) blank (4) blank$
D.
$(1) S \to B b B a (2) S \to A a A b (3) blank (4) blank$

Question 5 · Compiler Design · 2024_Set1 MCQ

Consider the following grammar

G

, with

S

as the start symbol. The grammar

G

has three incomplete productions denoted by (1), (2), and (3).

S \to d a T ∣ (1)

T \to a S ∣ b T ∣ (2)

R \to (3) ∣ ϵ

The set of terminals is

{a, b, c, d, f}

. The FIRST and FOLLOW sets of the different non-terminals are as follows.

FIRST (S) = {c, d, f}

FIRST (T) = {a, b, ϵ}

FIRST (R) = {c, ϵ}

FOLLOW (S) = FOLLOW (T) = {c, f, $}

FOLLOW (R) = {f}

Which one of the following options CORRECTLY fills in the incomplete productions?

A.
$(1) S \to R f (2) T \to ϵ (3) R \to c T R$
B.
$(1) S \to f R (2) T \to ϵ (3) R \to c T R$
C.
$(1) S \to f R (2) T \to c T (3) R \to c R$
D.
$(1) S \to R f (2) T \to c T (3) R \to c R$

Question 6 · Compiler Design · 2021_Set1 MCQ

Consider the following context-free grammar where the set of terminals is

{a, b, c, d, f}

S T R \to d a T ∣ R f \to a S ∣ ba T ∣ ϵ \to c a T R ∣ ϵ

The following is a partially-filled LL(1) parsing table.

	$a$	$b$	$c$	$d$	$f$	$$$
$S$			①	$S \to d a T$	②
$T$	$T \to a S$	$T \to ba T$	③		$T \to ϵ$	④
$R$			$R \to c a T R$		$R \to ϵ$

Which one of the following choices represents the correct combination for the numbered cells in the parsing table (“blank” denotes that the corresponding cell is empty)?

A.
① $S \to R f$ ② $S \to R f$ ③ $T \to ϵ$ ④ $T \to ϵ$
B.
① blank ② $S \to R f$ ③ $T \to ϵ$ ④ $T \to ϵ$
C.
① $S \to R f$ ② blank ③ blank ④ $T \to ϵ$
D.
① blank ② $S \to R f$ ③ blank ④ blank

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Questions calibrated to the real exam

Notes written for recall, not for volume

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Honest progress

Unlock the whole course

Top-Down and Predictive Parsing PYQs for GATE CS

Chapter Roadmap: Top-Down and Predictive Parsing

What are FIRST and FOLLOW, and why do they exist?

FIRST of A

FOLLOW of A

Top-Down and Predictive Parsing: Solved Questions with Step-by-Step Explanations (6 Problems)

More previous year questions (pyqs) in this unit

FIRST of $A$

FOLLOW of $A$