Probability Engine · CSC365

Compiler Design and Construction (BSc CSIT, CSC365): the questions likely to come

29 analyzed questions from 7 past papers (2074-2081), grouped by syllabus unit — each with its probability, how often it's been asked, and where to study the answer.

Papers analyzed

2074-2081

Analyzed questions

across 7 syllabus units

Very likely units

high-probability topics

Units = 80% of marks

study these first

Model answers for this subject are being written. Every question links to its original paper so you can study from the source meanwhile.

Pick a unit

U3 · Q1/10 · 208010 marks

Syntax Analysis (Parsing)

Explain top-down parsing. Construct the predictive (LL(1)) parsing table for the grammar E -> E+T | T, T -> T*F | F, F -> (E) | id after removing left recursion.

34%

Possible to appearAppeared in 2 of the last 2 board papers

Seen in

How well do you know this?rating moves you on

MODEL ANSWERU3 · 10 marks

Top-Down Parsing

Top-down parsing builds the parse tree from the root (start symbol) down to the leaves (terminals), attempting a leftmost derivation of the input. The two main approaches are:

Recursive-descent parsing (may use backtracking).
Predictive / LL(1) parsing — a non-backtracking, table-driven method that uses one symbol of look-ahead. It requires the grammar to be free of left recursion and to be left-factored.

Step 1: Remove Left Recursion

Given grammar:

E \to E+T \mid T, \quad T \to T*F \mid F, \quad F \to (E) \mid id

After eliminating left recursion:

E \to T\,E'

E' \to +T\,E' \mid \varepsilon

T \to F\,T'

T' \to *F\,T' \mid \varepsilon

F \to (E) \mid id

Step 2: FIRST and FOLLOW Sets

Non-terminal	FIRST	FOLLOW
$E$	{ (, id }	{ ), $ }
$E'$	{ +, $\varepsilon$ }	{ ), $ }
$T$	{ (, id }	{ +, ), $ }
$T'$	{ *, $\varepsilon$ }	{ +, ), $ }
$F$	{ (, id }	{ +, *, ), $ }

Step 3: LL(1) Predictive Parsing Table

Entry M[A, a] holds the production used when non-terminal $A$ is on the stack and $a$ is the look-ahead.

	id	+	*	(	)	$
E	$E\to TE'$			$E\to TE'$
E'		$E'\to +TE'$			$E'\to\varepsilon$	$E'\to\varepsilon$
T	$T\to FT'$			$T\to FT'$
T'		$T'\to\varepsilon$	$T'\to *FT'$		$T'\to\varepsilon$	$T'\to\varepsilon$
F	$F\to id$			$F\to (E)$

Blank cells denote error entries. Since no cell has more than one production, the grammar is LL(1) and can be parsed top-down without backtracking.

AI-generated answer · unverifiedView in 2080 paper →

U3 · Question 1 of 10

Question Priority · U3ranked by appearance likelihood — study top-down

Syntax Analysis (Parsing)

Analyzed next53%

★ TOP PICK

Explain top-down parsing. Construct the predictive (LL(1)) parsing table for the grammar E -> E+T | T, T -> T*F | F, F -> (E) | id after removing left recursion.

10 marksSEEN IN

34%

Explain the general structure of an LR parser. Construct the LR(0) item sets for the grammar S -> AA, A -> aA | b.

10 marksSEEN IN

30%

Construct the LR(1) parsing table for the grammar S -> CC, C -> cC | d and parse the input string cdd.

10 marksSEEN IN

28%

Eliminate left recursion and perform left factoring on the grammar A -> Aab | Ac | bd | f.

5 marksSEEN IN

53%

What is an ambiguous grammar? Show with an example.

5 marksSEEN IN

53%

Differentiate between LL(1) and LR parsers.

5 marksSEEN IN

53%

Explain the handle and handle pruning in shift-reduce parsing.

5 marksSEEN IN

53%

What is operator precedence parsing?

5 marksSEEN IN

42%

Differentiate between top-down and bottom-up parsing.

5 marksSEEN IN

42%

Differentiate between a parse tree and a syntax tree.

5 marksSEEN IN

26%

03The mock

Sit a probable paper

A full mock exam built from the most likely questions, mirroring the real paper's structure. Every slot is a real past question.

Most Probable Paper

Mirrors the real structure · 60 marks · based on 7 past papers

Section A: Long Answer QuestionsAttempt any TWO questions.

1.
Explain the different phases of a compiler with a suitable diagram, showing the output of each phase for the statement position = initial + rate * 60.
[10 marks]
IntroductionVery likelyfrom 2081 paper →
This question has recurred in 3 of 7 years; so far only in internal assessments, not the board; and its topic (Introduction) appears in 100% of years.
2.
Explain top-down parsing. Construct the predictive (LL(1)) parsing table for the grammar E -> E+T | T, T -> T*F | F, F -> (E) | id after removing left recursion.
[10 marks]
Syntax Analysis (Parsing)Very likelyfrom 2080 paper →
This question has recurred in 2 of 7 years; so far only in internal assessments, not the board; and its topic (Syntax Analysis (Parsing)) appears in 100% of years.
3.
Explain the general structure of an LR parser. Construct the LR(0) item sets for the grammar S -> AA, A -> aA | b.
[10 marks]
Syntax Analysis (Parsing)Very likelyfrom 2079 paper →
This question has recurred in 2 of 7 years; so far only in internal assessments, not the board; and its topic (Syntax Analysis (Parsing)) appears in 100% of years.

Section B: Short Answer QuestionsAttempt any EIGHT questions.

1.
Eliminate left recursion and perform left factoring on the grammar A -> Aab | Ac | bd | f.
[5 marks]
Syntax Analysis (Parsing)Very likelyfrom 2081 paper →
This question has recurred in 4 of 7 years; so far only in internal assessments, not the board; and its topic (Syntax Analysis (Parsing)) appears in 100% of years.
2.
What is an ambiguous grammar? Show with an example.
[5 marks]
Syntax Analysis (Parsing)Very likelyfrom 2081 paper →
This question has recurred in 4 of 7 years; so far only in internal assessments, not the board; and its topic (Syntax Analysis (Parsing)) appears in 100% of years.
3.
Differentiate between LL(1) and LR parsers.
[5 marks]
Syntax Analysis (Parsing)Very likelyfrom 2081 paper →
This question has recurred in 4 of 7 years; so far only in internal assessments, not the board; and its topic (Syntax Analysis (Parsing)) appears in 100% of years.
4.
Explain the handle and handle pruning in shift-reduce parsing.
[5 marks]
Syntax Analysis (Parsing)Very likelyfrom 2081 paper →
This question has recurred in 4 of 7 years; so far only in internal assessments, not the board; and its topic (Syntax Analysis (Parsing)) appears in 100% of years.
5.
Differentiate between a compiler and an interpreter.
[5 marks]
IntroductionVery likelyfrom 2081 paper →
This question has recurred in 4 of 7 years; so far only in internal assessments, not the board; and its topic (Introduction) appears in 100% of years.
6.
What is a symbol table? Explain its role in a compiler.
[5 marks]
IntroductionVery likelyfrom 2081 paper →
This question has recurred in 4 of 7 years; so far only in internal assessments, not the board; and its topic (Introduction) appears in 100% of years.
7.
Explain the role of the lexical analyzer in a compiler.
[5 marks]
Lexical AnalysisVery likelyfrom 2081 paper →
This question has recurred in 4 of 7 years; so far only in internal assessments, not the board; and its topic (Lexical Analysis) appears in 100% of years.
8.
What are regular expressions? Write a regular expression for identifiers.
[5 marks]
Lexical AnalysisVery likelyfrom 2081 paper →
This question has recurred in 4 of 7 years; so far only in internal assessments, not the board; and its topic (Lexical Analysis) appears in 100% of years.
9.
What is operator precedence parsing?
[5 marks]
Syntax Analysis (Parsing)Very likelyfrom 2080 paper →
This question has recurred in 3 of 7 years; so far only in internal assessments, not the board; and its topic (Syntax Analysis (Parsing)) appears in 100% of years.

04The receipts

Behind the numbers

The raw evidence the predictions are computed from: marks per unit per year, syllabus weights, trends, and coverage.

Show the heatmap, topic table and coverage analysis

The receipt: marks per unit, per year

Each row is a syllabus unit, each column an exam year, each cell the marks that unit earned that year. Click any cell to see the actual questions behind it.

Marks:nonefew → many

2074

2075

2077

2078

2079

2080

2081

Total

U3Syntax Analysis (Parsing)

180

U1Introduction

U2Lexical Analysis

U4Syntax-Directed Translation

U6Code Optimization

U5Intermediate Code Generation

U7Code Generation

#	Syllabus unit	Probability	Appeared	Avg marks	Syllabus weight	Exam vs syllabus	Trend	Questions
1	U3Syntax Analysis (Parsing)	Very likely100%	2074 2075 2077 2078 2079 2080 2081	25.7	31%14 lecture hrs	Balancedexam 34% · syllabus 31%	Fading	10 recurring10 total
2	U1Introduction	Very likely100%	2074 2075 2077 2078 2079 2080 2081	12.1	9%4 lecture hrs	Over-examinedexam 16% · syllabus 9%	Steady	4 recurring4 total
3	U2Lexical Analysis	Very likely100%	2074 2075 2077 2078 2079 2080 2081	10.7	18%8 lecture hrs	Balancedexam 14% · syllabus 18%	Steady	4 recurring4 total
4	U4Syntax-Directed Translation	Likely71%	2075 2078 2079 2080 2081	13	13%6 lecture hrs	Balancedexam 12% · syllabus 13%	Steady	4 recurring4 total
5	U6Code Optimization	Likely57%	2075 2077 2078 2080	12.5	9%4 lecture hrs	Balancedexam 10% · syllabus 9%	Steady	3 recurring3 total
6	U5Intermediate Code Generation	Likely71%	2074 2075 2078 2079 2080	7	13%6 lecture hrs	Under-examinedexam 7% · syllabus 13%	Steady	2 recurring2 total
7	U7Code Generation	Likely71%	2075 2077 2078 2080 2081	7	7%3 lecture hrs	Balancedexam 7% · syllabus 7%	Steady	2 recurring2 total

Study smart, not hard

Drag the slider: studying the top 5 units in priority order covers ~87% of all observed marks.

Units to study5/7

~80% line

Lecture time vs exam marks

Where the exam pays more than the curriculum spends: ● lectures vs ● exam marks, as a share of the whole course. A long teal-leading bar = high-yield unit.

U3Syntax Analysis (Parsing)

31% of lectures → 34% of marks

U1Introduction

9% of lectures → 16% of markshigh yield

U2Lexical Analysis

18% of lectures → 14% of marks

U4Syntax-Directed Translation

13% of lectures → 12% of marks

U6Code Optimization

9% of lectures → 10% of marks

U5Intermediate Code Generation

13% of lectures → 7% of markslow yield

U7Code Generation

7% of lectures → 7% of marks

Compiler Design and Construction (BSc CSIT, CSC365): the questions likely to come

Top-Down Parsing

Step 1: Remove Left Recursion

Step 2: FIRST and FOLLOW Sets

Step 3: LL(1) Predictive Parsing Table

Syntax Analysis (Parsing)

Sit a probable paper

Most Probable Paper

Behind the numbers

The receipt: marks per unit, per year

Study smart, not hard

Lecture time vs exam marks

2081 B.S.

Compiler Design and Construction (BSc CSIT, CSC365)

2080 B.S.

Compiler Design and Construction (BSc CSIT, CSC365)

2079 B.S.

Compiler Design and Construction (BSc CSIT, CSC365)

2078 B.S.

Compiler Design and Construction (BSc CSIT, CSC365)

2077 B.S.

Compiler Design and Construction (BSc CSIT, CSC365)

2075 B.S.

Compiler Design and Construction (BSc CSIT, CSC365)

2074 B.S.

Compiler Design and Construction (BSc CSIT, CSC365)