“Top 100 Compiler Design MCQs with Answers 2026”

 “Top 100 Compiler Design MCQs with Answers 2026”

Prepare smarter for exams with MCQ Journey’s Top 100 Compiler Design MCQs with Answers 2026. This comprehensive collection of multiple‑choice questions is designed for Computer Science students, engineering aspirants, and competitive exam candidates preparing for GATE, UGC NET, university tests, and technical interviews. Each MCQ is carefully curated to cover essential topics in compiler design, including lexical analysis, syntax analysis, parsing, code generation, and optimization. With detailed answers provided, learners can practice effectively, strengthen conceptual clarity, and improve exam performance. Whether you are revising for semester exams, brushing up for interviews, or preparing for national‑level competitive exams, these exam‑oriented practice questions offer the perfect blend of theory and application. Trusted by thousands of students, MCQ Journey ensures student‑friendly explanations, exam‑relevant coverage, and authoritative content to help you succeed. Start practicing today and boost your confidence with this unique set of compiler design MCQs with answers for 2026 exam preparation.

📝 MCQs 

Q1. Which phase of the compiler converts source code into tokens? A. Syntax Analysis B. Lexical Analysis C. Semantic Analysis D. Code Generation Answer: B Explanation: Lexical analysis scans the source code and breaks it into tokens.

Q2. Which data structure is commonly used in recursive descent parsing? A. Queue B. Stack C. Linked List D. Tree Answer: B Explanation: Stack helps manage recursive calls during parsing.

Q3. In compiler design, which grammar is used for syntax analysis? A. Context-Free Grammar B. Regular Grammar C. Phrase Structure Grammar D. Finite Grammar Answer: A

Q4. Which optimization technique eliminates common sub-expressions? A. Constant Folding B. Dead Code Elimination C. Common Subexpression Elimination D. Loop Unrolling Answer: C

Q5. Which parsing technique is used in LR parsers? A. Top-Down Parsing B. Bottom-Up Parsing C. Recursive Parsing D. Predictive Parsing Answer: B

Q6. Which of the following is NOT a phase of a compiler? A. Lexical Analysis B. Syntax Analysis C. Debugging D. Code Optimization Answer: C Explanation: Debugging is part of software development, not compiler phases.

Q7. The output of lexical analysis is stored in which structure? A. Symbol Table B. Parse Tree C. Token Stream D. Intermediate Code Answer: C

Q8. Which parsing method uses lookahead symbols to make decisions? A. LL Parsing B. LR Parsing C. Recursive Descent Parsing D. Operator Precedence Parsing Answer: B

Q9. Which compiler phase checks type compatibility? A. Lexical Analysis B. Syntax Analysis C. Semantic Analysis D. Code Generation Answer: C

Q10. Which of the following is a machine‑independent optimization? A. Register Allocation B. Instruction Scheduling C. Constant Folding D. Peephole Optimization Answer: C

Q11. Which data structure is used to store identifiers and their attributes? A. Stack B. Queue C. Symbol Table D. Hash Map Answer: C

Q12. Which grammar cannot be parsed using LL(1) parsers? A. Ambiguous Grammar B. Context‑Free Grammar C. Regular Grammar D. Left‑Recursive Grammar Answer: D

Q13. Which intermediate representation is commonly used in compilers? A. Abstract Syntax Tree B. Machine Code C. Assembly Code D. Object Code Answer: A

Q14. Which optimization technique removes unreachable code? A. Dead Code Elimination B. Loop Unrolling C. Constant Propagation D. Strength Reduction Answer: A

Q15. Which parsing technique is most suitable for programming languages? A. LL Parsing B. LR Parsing C. Operator Precedence Parsing D. Recursive Descent Parsing Answer: B

Q16. Which of the following is responsible for detecting syntax errors? A. Lexical Analyzer B. Syntax Analyzer C. Semantic Analyzer D. Code Optimizer Answer: B

Q17. Which compiler phase generates intermediate code? A. Lexical Analysis B. Syntax Analysis C. Semantic Analysis D. Code Generation Answer: D

Q18. Which of the following is NOT a type of parser? A. LL Parser B. LR Parser C. Recursive Descent Parser D. Hash Parser Answer: D

Q19. Which optimization technique reduces strength of operations? A. Constant Folding B. Strength Reduction C. Dead Code Elimination D. Loop Unrolling Answer: B

Q20. Which of the following is a bottom‑up parser? A. LL(1) Parser B. LR Parser C. Recursive Descent Parser D. Predictive Parser Answer: B

Q21. Which compiler phase ensures variables are declared before use? A. Lexical Analysis B. Syntax Analysis C. Semantic Analysis D. Code Optimization Answer: C

Q22. Which of the following is used for error recovery in parsing? A. Panic Mode B. Loop Unrolling C. Constant Folding D. Dead Code Elimination Answer: A

Q23. Which intermediate code form uses three addresses? A. Quadruples B. Triples C. Three‑Address Code D. Abstract Syntax Tree Answer: C

Q24. Which optimization technique propagates known values? A. Constant Propagation B. Dead Code Elimination C. Loop Optimization D. Peephole Optimization Answer: A

Q25. Which of the following is a top‑down parsing technique? A. LR Parsing B. LL Parsing C. Bottom‑Up Parsing D. Operator Precedence Parsing Answer: B

Q26. Which of the following is NOT a type of intermediate code representation? A. Quadruples B. Triples C. Three‑Address Code D. Binary Machine Code Answer: D

Q27. Which compiler phase is responsible for building the parse tree? A. Lexical Analysis B. Syntax Analysis C. Semantic Analysis D. Code Generation Answer: B

Q28. Which optimization technique reduces loop overhead? A. Loop Unrolling B. Dead Code Elimination C. Constant Folding D. Strength Reduction Answer: A

Q29. Which of the following is a bottom‑up parsing method? A. Recursive Descent Parsing B. LL Parsing C. LR Parsing D. Predictive Parsing Answer: C

Q30. Which compiler phase checks for undeclared variables? A. Lexical Analysis B. Syntax Analysis C. Semantic Analysis D. Code Optimization Answer: C

Q31. Which of the following is a machine‑dependent optimization? A. Constant Folding B. Dead Code Elimination C. Register Allocation D. Common Subexpression Elimination Answer: C

Q32. Which parsing technique uses FIRST and FOLLOW sets? A. LL Parsing B. LR Parsing C. Operator Precedence Parsing D. Recursive Descent Parsing Answer: A

Q33. Which compiler phase generates assembly code? A. Lexical Analysis B. Syntax Analysis C. Code Generation D. Semantic Analysis Answer: C

Q34. Which of the following is NOT an error type in compilers? A. Lexical Error B. Syntax Error C. Semantic Error D. Hardware Error Answer: D

Q35. Which optimization technique replaces expensive operations with cheaper ones? A. Strength Reduction B. Dead Code Elimination C. Constant Folding D. Loop Optimization Answer: A

Q36. Which of the following is used to detect semantic errors? A. Lexical Analyzer B. Syntax Analyzer C. Semantic Analyzer D. Code Generator Answer: C

Q37. Which optimization technique removes redundant calculations? A. Common Subexpression Elimination B. Dead Code Elimination C. Constant Folding D. Loop Unrolling Answer: A

Q38. Which of the following is NOT a parsing technique? A. LL Parsing B. LR Parsing C. Recursive Descent Parsing D. Binary Search Parsing Answer: D

Q39. Which compiler phase generates machine‑independent code? A. Lexical Analysis B. Syntax Analysis C. Intermediate Code Generation D. Code Optimization Answer: C

Q40. Which of the following is a top‑down parser? A. LR Parser B. LL Parser C. Operator Precedence Parser D. Bottom‑Up Parser Answer: B

Q41. Which optimization technique simplifies constant expressions at compile time? A. Constant Folding B. Dead Code Elimination C. Loop Optimization D. Strength Reduction Answer: A

Q42. Which compiler phase is responsible for symbol table management? A. Lexical Analysis B. Syntax Analysis C. Semantic Analysis D. All of the above Answer: D

Q43. Which of the following is NOT a compiler optimization technique? A. Loop Unrolling B. Constant Propagation C. Dead Code Elimination D. Debugging Answer: D

Q44. Which parsing technique is most widely used in modern compilers? A. LL Parsing B. LR Parsing C. Recursive Descent Parsing D. Operator Precedence Parsing Answer: B

Q45. Which compiler phase translates intermediate code into target machine code? A. Lexical Analysis B. Syntax Analysis C. Code Generation D. Semantic Analysis Answer: C

Q46. Which of the following is NOT a valid parsing technique? A. LL Parsing B. LR Parsing C. Recursive Descent Parsing D. Binary Tree Parsing Answer: D

Q47. Which compiler phase checks the scope of variables? A. Lexical Analysis B. Syntax Analysis C. Semantic Analysis D. Code Generation Answer: C

Q48. Which optimization technique reduces loop iterations? A. Loop Unrolling B. Dead Code Elimination C. Constant Folding D. Strength Reduction Answer: A

Q49. Which of the following is a bottom‑up parsing technique? A. LL Parsing B. LR Parsing C. Recursive Descent Parsing D. Predictive Parsing Answer: B

Q50. Which compiler phase generates target machine code? A. Lexical Analysis B. Syntax Analysis C. Code Generation D. Semantic Analysis Answer: C

Q51. Which optimization technique removes unnecessary computations? A. Common Subexpression Elimination B. Dead Code Elimination C. Constant Propagation D. Loop Optimization Answer: A

Q52. Which compiler phase ensures type compatibility? A. Lexical Analysis B. Syntax Analysis C. Semantic Analysis D. Code Optimization Answer: C

Q53. Which of the following is NOT an intermediate code representation? A. Quadruples B. Triples C. Three‑Address Code D. Binary Machine Code Answer: D

Q54. Which parsing technique uses predictive methods? A. LL Parsing B. LR Parsing C. Operator Precedence Parsing D. Bottom‑Up Parsing Answer: A

Q55. Which optimization technique propagates constant values throughout the program? A. Constant Folding B. Constant Propagation C. Dead Code Elimination D. Strength Reduction Answer: B

Q56. Which compiler phase is responsible for detecting undeclared identifiers? A. Lexical Analysis B. Syntax Analysis C. Semantic Analysis D. Code Generation Answer: C

Q57. Which optimization technique eliminates instructions that have no effect on program output? A. Dead Code Elimination B. Constant Folding C. Strength Reduction D. Loop Optimization Answer: A

Q58. Which of the following is NOT a bottom‑up parsing technique? A. LR Parsing B. Operator Precedence Parsing C. LL Parsing D. Shift‑Reduce Parsing Answer: C

Q59. Which compiler phase generates intermediate representation of the source code? A. Lexical Analysis B. Syntax Analysis C. Intermediate Code Generation D. Code Optimization Answer: C

Q60. Which optimization technique replaces multiplication with addition? A. Constant Folding B. Strength Reduction C. Dead Code Elimination D. Loop Unrolling Answer: B

Q61. Which of the following is used for error recovery in compilers? A. Panic Mode B. Constant Folding C. Loop Optimization D. Dead Code Elimination Answer: A

Q62. Which compiler phase checks for type mismatches? A. Lexical Analysis B. Syntax Analysis C. Semantic Analysis D. Code Generation Answer: C

Q63. Which intermediate code representation uses tuples of four fields? A. Quadruples B. Triples C. Three‑Address Code D. Abstract Syntax Tree Answer: A

Q64. Which optimization technique simplifies algebraic identities? A. Constant Folding B. Algebraic Simplification C. Dead Code Elimination D. Loop Optimization Answer: B

Q65. Which parsing technique is most suitable for deterministic context‑free grammars? A. LL Parsing B. LR Parsing C. Recursive Descent Parsing D. Operator Precedence Parsing Answer: B

Q66. Which compiler phase is responsible for generating optimized intermediate code? A. Lexical Analysis B. Syntax Analysis C. Code Optimization D. Semantic Analysis Answer: C

Q67. Which parsing technique uses a predictive table for decision making? A. LL(1) Parsing B. LR Parsing C. Operator Precedence Parsing D. Recursive Descent Parsing Answer: A

Q68. Which optimization technique removes duplicate computations within loops? A. Loop Invariant Code Motion B. Dead Code Elimination C. Constant Folding D. Strength Reduction Answer: A

Q69. Which compiler phase generates the symbol table? A. Lexical Analysis B. Syntax Analysis C. Semantic Analysis D. Intermediate Code Generation Answer: A

Q70. Which of the following is NOT a bottom‑up parsing technique? A. LR Parsing B. Operator Precedence Parsing C. LL Parsing D. Shift‑Reduce Parsing Answer: C

Q71. Which optimization technique replaces repeated expressions with temporary variables? A. Common Subexpression Elimination B. Constant Folding C. Dead Code Elimination D. Loop Optimization Answer: A

Q72. Which compiler phase ensures correct usage of operators and operands? A. Lexical Analysis B. Syntax Analysis C. Semantic Analysis D. Code Generation Answer: C

Q73. Which intermediate representation uses tuples of three fields? A. Quadruples B. Triples C. Three‑Address Code D. Abstract Syntax Tree Answer: B

Q74. Which optimization technique reduces loop overhead by duplicating loop body? A. Loop Unrolling B. Dead Code Elimination C. Constant Propagation D. Strength Reduction Answer: A

Q75. Which parsing technique is most suitable for programming languages with complex grammars? A. LL Parsing B. LR Parsing C. Recursive Descent Parsing D. Operator Precedence Parsing Answer: B

Q76. Which compiler phase is responsible for generating target assembly code? A. Lexical Analysis B. Syntax Analysis C. Code Generation D. Semantic Analysis Answer: C

Q77. Which optimization technique moves loop‑invariant computations outside the loop? A. Loop Invariant Code Motion B. Dead Code Elimination C. Constant Folding D. Strength Reduction Answer: A

Q78. Which parsing technique uses shift and reduce operations? A. LL Parsing B. LR Parsing C. Recursive Descent Parsing D. Predictive Parsing Answer: B

Q79. Which compiler phase checks for semantic consistency in programs? A. Lexical Analysis B. Syntax Analysis C. Semantic Analysis D. Code Optimization Answer: C

Q80. Which optimization technique replaces costly operations with simpler ones? A. Strength Reduction B. Constant Folding C. Dead Code Elimination D. Loop Optimization Answer: A

Q81. Which intermediate representation is widely used for optimization? A. Abstract Syntax Tree B. Three‑Address Code C. Machine Code D. Object Code Answer: B

Q82. Which compiler phase manages scope and binding of identifiers? A. Lexical Analysis B. Syntax Analysis C. Semantic Analysis D. Code Generation Answer: C

Q83. Which optimization technique removes instructions that never execute? A. Dead Code Elimination B. Constant Folding C. Loop Optimization D. Strength Reduction Answer: A

Q84. Which parsing technique is most suitable for deterministic grammars? A. LL Parsing B. LR Parsing C. Recursive Descent Parsing D. Operator Precedence Parsing Answer: B

Q85. Which compiler phase translates high‑level code into machine code? A. Lexical Analysis B. Syntax Analysis C. Code Generation D. Semantic Analysis Answer: C

Q86. Which compiler phase checks for semantic consistency of expressions? A. Lexical Analysis B. Syntax Analysis C. Semantic Analysis D. Code Generation Answer: C

Q87. Which optimization technique eliminates redundant code sequences? A. Dead Code Elimination B. Common Subexpression Elimination C. Constant Folding D. Loop Optimization Answer: B

Q88. Which parsing technique is based on recursive procedures for non‑terminals? A. LL Parsing B. LR Parsing C. Recursive Descent Parsing D. Operator Precedence Parsing Answer: C

Q89. Which compiler phase generates machine‑independent intermediate code? A. Lexical Analysis B. Syntax Analysis C. Intermediate Code Generation D. Code Optimization Answer: C

Q90. Which optimization technique removes instructions that do not affect program output? A. Dead Code Elimination B. Constant Folding C. Strength Reduction D. Loop Unrolling Answer: A

Q91. Which intermediate representation uses tuples of four fields? A. Quadruples B. Triples C. Three‑Address Code D. Abstract Syntax Tree Answer: A

Q92. Which compiler phase ensures correct type conversions? A. Lexical Analysis B. Syntax Analysis C. Semantic Analysis D. Code Generation Answer: C

Q93. Which optimization technique propagates constant values across assignments? A. Constant Folding B. Constant Propagation C. Dead Code Elimination D. Strength Reduction Answer: B

Q94. Which parsing technique is most suitable for bottom‑up grammar analysis? A. LL Parsing B. LR Parsing C. Recursive Descent Parsing D. Predictive Parsing Answer: B

Q95. Which compiler phase translates intermediate code into target machine instructions? A. Lexical Analysis B. Syntax Analysis C. Code Generation D. Semantic Analysis Answer: C

Q96. Which compiler phase is responsible for final code translation into machine language? A. Lexical Analysis B. Syntax Analysis C. Code Generation D. Semantic Analysis Answer: C

Q97. Which optimization technique eliminates repeated calculations across different parts of a program? A. Common Subexpression Elimination B. Dead Code Elimination C. Constant Folding D. Loop Optimization Answer: A

Q98. Which parsing technique is most suitable for bottom‑up grammar analysis in compilers? A. LL Parsing B. LR Parsing C. Recursive Descent Parsing D. Predictive Parsing Answer: B

Q99. Which compiler phase ensures correct binding of identifiers and scope resolution? A. Lexical Analysis B. Syntax Analysis C. Semantic Analysis D. Code Optimization Answer: C

Q100. Which optimization technique duplicates loop body to reduce iteration overhead? A. Loop Unrolling B. Dead Code Elimination C. Constant Propagation D. Strength Reduction Answer: A

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