Grammar and Compilation Quiz
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Questions and Answers

What is the primary function of Type-1 grammars?

  • Generate context-sensitive languages. (correct)
  • Generate recursively enumerable languages.
  • Generate context-free languages.
  • Generate regular languages.

Which of the following production forms is valid for Type-1 grammars?

  • γ → α
  • S → ε where S appears on the right
  • A → α β
  • α A β → α γ β (correct)

What type of automaton recognizes the languages generated by Type-1 grammars?

  • Finite state automaton.
  • Pushdown automaton.
  • Linear bounded automaton. (correct)
  • Turing machine.

Which grammars can generate structures without restrictions on productions?

<p>Type-0 grammars. (B)</p> Signup and view all the answers

What is the purpose of lexical analysis in the compilation process?

<p>Identify and categorize tokens from the input stream. (D)</p> Signup and view all the answers

How are tokens recognized in the input stream during lexical analysis?

<p>Using regular expressions and state machines. (C)</p> Signup and view all the answers

What is the form of a production rule in grammar?

<p>α → β (D)</p> Signup and view all the answers

Which of the following is NOT a phase in the compilation process?

<p>Error Prevention. (D)</p> Signup and view all the answers

Which of the following is a characteristic of Type-3 grammars?

<p>Generate regular languages (C)</p> Signup and view all the answers

In the context of Type-0 grammars, what is the significance of the string α?

<p>It must include at least one non-terminal. (D)</p> Signup and view all the answers

Which production demonstrates the use of epsilon in a grammar?

<p>Y → ε (C)</p> Signup and view all the answers

What kind of languages can Type-2 grammars generate?

<p>Context-free languages (D)</p> Signup and view all the answers

Which of the following productions is a valid production for a Type-3 grammar?

<p>X → aY (A)</p> Signup and view all the answers

In which of the following grammars does 'S' not appear on the right side of any rule?

<p>G2 (C)</p> Signup and view all the answers

Given the production S → aAb, which of the following strings cannot be derived?

<p>ab (D)</p> Signup and view all the answers

What is the main difference between Type-1 and Type-2 grammars?

<p>Type-2 requires specific forms of productions. (B)</p> Signup and view all the answers

What is the primary function of lexical analysis in a compiler?

<p>To recognize tokens and specify them (B)</p> Signup and view all the answers

A grammar can be formally represented as which of the following?

<p>A 4-tuple (N, T, S, P) (C)</p> Signup and view all the answers

Which type of grammar is primarily used in the context-free grammars employed in syntax analysis?

<p>Context-free grammar (B)</p> Signup and view all the answers

What are Syntax Directed Translation Schemes (SDTS) used for?

<p>To facilitate the translation of code segments (B)</p> Signup and view all the answers

Which parsing technique is recognized as more powerful than traditional parsers?

<p>LR parsing (B)</p> Signup and view all the answers

In code generation, what is the role of 3-address code?

<p>It represents computations with at most three operands (D)</p> Signup and view all the answers

What is a primary function of a preprocessor in a programming environment?

<p>To include header files and define macros (A)</p> Signup and view all the answers

What does the 'Target Language Address' refer to in code generation?

<p>The location of variables in memory (C)</p> Signup and view all the answers

What is a manifest constant in programming?

<p>An identifier declared to represent a constant value (A)</p> Signup and view all the answers

Which parsing technique starts with the starting symbol and moves down to the tree leaves?

<p>Top-down parsing (B)</p> Signup and view all the answers

In context-free grammar, what does 'T' represent?

<p>Terminal symbols (D)</p> Signup and view all the answers

What is the role of a parser in a compiler?

<p>To verify and report syntax of tokens (A)</p> Signup and view all the answers

Which of the following statements about bottom-up parsing is true?

<p>It begins at the tree leaves and moves upward to the root. (A)</p> Signup and view all the answers

What problem does backtracking in recursive descent parsing aim to solve?

<p>Recovering from failed derivations by trying different production rules (B)</p> Signup and view all the answers

Which components are included in the declarations section of a Lex program?

<p>Variables, manifest constants, and regular definitions (C)</p> Signup and view all the answers

In context-free grammar, what does the intersection condition 'N ∩ T = NULL' indicate?

<p>Non-terminals and terminals cannot share symbols (C)</p> Signup and view all the answers

What is the purpose of temporary names in code generation?

<p>To enable code optimization and facilitate easy relocation. (B)</p> Signup and view all the answers

Which instruction can set the value of a variable to the address of another variable?

<p>x = &amp;y (B)</p> Signup and view all the answers

What occurs during an unconditional jump instruction?

<p>Control transfers to a specific label unconditionally. (C)</p> Signup and view all the answers

In three address code, which of the following is an example of a copy instruction?

<p>x = y (A)</p> Signup and view all the answers

What does the back patching technique help solve in code generation?

<p>The issue of unknown target labels in jumps. (A)</p> Signup and view all the answers

Which function in the back patching process is responsible for creating a new list?

<p>makelist(i) (C)</p> Signup and view all the answers

When using indexed copy instructions, what does 'x = y[i]' accomplish?

<p>Sets x to the value at position i in y. (B)</p> Signup and view all the answers

What type of operation does the unary operator '!' perform in three address code?

<p>Negation of a value. (D)</p> Signup and view all the answers

What is the purpose of inherited attributes in compiler design?

<p>They are derived from the attributes of both siblings and parent nodes. (C)</p> Signup and view all the answers

Which traversal method is used in S-Attributed Definitions for semantic rule evaluation?

<p>PostOrder traversal (D)</p> Signup and view all the answers

What distinguishes high-level intermediate representations in compilers?

<p>They are closer to the source language. (A)</p> Signup and view all the answers

What is a significant characteristic of low-level intermediate representations?

<p>They facilitate register allocation and instruction selection. (C)</p> Signup and view all the answers

What does the term 'three-address code' refer to in compiler design?

<p>A sequence of instructions, each with up to three addresses. (D)</p> Signup and view all the answers

What types of addresses can be used in three-address code?

<p>Identities, constants, or temporary addresses. (C)</p> Signup and view all the answers

What is the role of static checking in the compiler front end?

<p>To identify structural errors within the code. (B)</p> Signup and view all the answers

How does intermediate representation assist in compiler design?

<p>It bridges the gap between source and target languages. (A)</p> Signup and view all the answers

Flashcards

Grammar

A set of rules that define the structure of a language.

Formal Grammar

A formal way to represent a grammar using four components: non-terminal symbols, terminal symbols, a start symbol, and production rules.

Non-terminal Symbols

Symbols that represent parts of a language that can be broken down further.

Terminal Symbols

Symbols that represent the basic building blocks of a language.

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Start Symbol

A special non-terminal symbol that represents the starting point of a language.

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Production Rules

Rules that dictate how to combine terminal and non-terminal symbols to create valid sentences.

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Context-Free Grammar

A special type of grammar where the production rules are context-free, meaning they are not limited by the surrounding symbols.

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Grammar for Programming Languages

Using a formal grammar to specify the syntax of a computer programming language.

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String in Formal Grammars

A sequence of symbols, terminals and non-terminals, used in formal grammars. Think of it like a chain of characters with specific rules.

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Derivation

The process of applying production rules to a starting symbol to derive a sequence of strings in a grammar. Think of it as building a sentence step by step.

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Chomsky Hierarchy

Type of formal grammar where the production rules have specific limitations, generating a specific type of language.

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Type-3 Grammar

Formal grammars that can generate regular languages, characterized by production rules with only one non-terminal on the left side and a single terminal or terminal followed by a non-terminal on the right side.

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Type - 2 Grammar

Formal grammars that can generate context-free languages, characterized by production rules with a single non-terminal on the left side and any combination of terminals and non-terminals on the right side.

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String

A sequence of characters.

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Analysis Phase

The process of analyzing the source code to understand its structure and meaning. This is generally broken down into lexical analysis, syntax analysis and intermediate code generation.

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Synthesis Phase

The process of converting the intermediate code into machine code that can be executed by the target computer. This includes code optimization and the generation of machine-specific instructions.

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Lexical Analysis

The first step in compiling, where the source code is scanned to identify individual units (tokens). It also handles comments and ignores whitespaces.

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Syntax Analysis

The process of verifying the grammatical correctness of the source code according to the rules of the programming language. It ensures the code follows the syntax rules.

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Declarations Section

A section of code that declares variables, constants, and regular definitions.

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Translation Rules

Rules that define how to translate a Lex program's input into tokens.

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Auxiliary Procedures

Procedures used by action routines in a Lex program. They can be compiled separately or included within the analyzer.

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Parser

A program that analyzes the structure of a source program and checks for errors. It ensures the input is properly formatted according to the language's syntax.

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Top-Down Parsing

A parsing technique that starts with the starting symbol and works its way down to the tree leaves, using productions.

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Bottom-Up Parsing

A parsing technique that starts at the tree leaves and works its way up to the root, which is the start symbol.

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Inherited Attributes

Attributes that are calculated based on the values of both the sibling and parent nodes in a tree structure. They provide a way to represent the combined information from related parts of a data structure.

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Syntax Directed Definition

A method in compiler design that associates attributes with each non-terminal symbol in a grammar. These attributes represent semantic information and can be used to perform various actions, such as type checking, code generation, or even error detection.

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S-Attributed Definitions

A type of Syntax Directed Definition where attributes are only computed from the values of the children nodes. They are calculated in a bottom-up manner.

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Intermediate Code Generation

An intermediate representation of source code that is independent of the target machine architecture. It simplifies the optimization process and facilitates the creation of compilers for different architectures.

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Static Checking

The process of ensuring that a program adheres to the rules of the programming language, including type consistency, proper variable usage, and correct control flow structures.

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Low Level Representations

A representation of the source program that is closer to the target machine. It facilitates optimizations and code generation.

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High Level Representations

A representation of the source program that is closer to the source language itself. It is useful for early optimizations and facilitating code generation.

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3-Address Code (TAC)

A language-independent intermediate representation that uses a sequence of three-address instructions to express the program's logic. Each instruction has up to three addresses, typically representing variables, constants or temporary values.

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Temporary Names

Temporary names used for code optimization, easily moved during compilation.

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Three-Address Code (TAC) Instructions

Instructions generated during compilation that represent basic operations like arithmetic, logical, and data transfer.

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Binary Arithmetic and Logical Operations in TAC

Includes operations like addition, subtraction, multiplication, division, AND, OR, and XOR.

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Unary Arithmetic and Logical Operations in TAC

Includes unary operations like negation (-) for arithmetic and logical negation (!) for boolean values. Also includes type conversion between data types.

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Copy Instructions in TAC

Simple data transfer instruction. Copies the value of one operand to another. Example: x=y

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Unconditional Jump Instruction in TAC

Unconditional jump to a specific labeled instruction. Example: goto L

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Label in TAC Instructions

A symbolic label assigned to an instruction in TAC, used as a target for jump instructions.

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Function Call Instructions in TAC

Instructions for function call and return. Example: y=p(x1,..., xn)

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Study Notes

Compiler Design

  • A compiler is a program that translates source code (written in a high-level language) into equivalent target code (often machine code).
  • The process involves multiple phases, including lexical analysis, syntax analysis, semantic analysis, intermediate code generation, optimization, and code generation.
  • Grammar types, such as context-free grammars, are used to define the structure of the source language.
  • Lexical analysis breaks the source code into tokens.
  • Syntax analysis verifies the structure of the code, using a grammar.
  • Semantic analysis checks the meaning of the code, such as type compatibility.
  • Intermediate code generation creates an intermediate representation of the source code, often a low-level representation.
  • Optimization improves the efficiency of the intermediate code.
  • Code generation translates the optimized intermediate code into the target code.
  • The compiler must handle errors during each phase.
  • Compiler phases include analysis and synthesis.
  • The analysis phase (machine independent / language dependent) translates the source code into an intermediate representation.
  • The synthesis phase (machine dependent/ language independent) generates the target code from the intermediate representation.

Lexical Analysis

  • The lexical analyzer, also called a scanner, reads the input character by character to determine tokens.
  • Takes the stream of characters and creates tokens, one by one.
  • A token is a sequence of characters representing a meaningful unit in the programming language (e.g., keywords, identifiers, operators).
  • Patterns define the set of strings that belong to one token type, written using regular expressions
  • A lexeme is an actual sequence of characters that matches a pattern.
  • Lexeme is the keyword, identifier or constant.
  • Example:
    • Token: if
    • Lexeme: if
    • Pattern: if

Syntax Analysis

  • The syntax analyzer or parser takes tokens and constructs a parse tree according to the grammar rules.
  • It checks whether the code is syntactically correct.
  • Two common parsing methods are top-down parsing and bottom-up parsing.
  • The parser constructs an abstract syntax tree (AST)
  • Example: if statement has clauses, conditions, and statements.

Semantic Analysis

  • Semantic analysis checks the meaning of the code.
  • It verifies the consistency and correctness of the code according to the language's semantic rules.
  • It performs type checking to ensure that operations are performed on compatible types.
  • It checks for various semantic errors.
  • It generates symbol tables with information about symbols found in the source code.

Intermediate Code Generation

  • An intermediate code is a representation of the source code in a form that's more suitable for translation to machine code in the next stage.
  • Often a simpler form than the original source code but more structured than the target code.
  • Various intermediate representations exist:
    • Three-address code (TAC).
    • Triples.
    • Quadruples

Code Optimization

  • Optimization improves the efficiency of the intermediate code
  • Code optimization can involve various transformations, such as:
    • Constant folding.
    • Common subexpression elimination.
    • Dead code elimination.
    • Copy propagation.

Code Generation

  • Transforms the intermediate code into target code (machine code or assembly code).
  • The target code is machine-dependent.

Runtime Environments

  • The runtime environment manages the execution of a program.
  • Components include:
    • Stack allocation.
    • Heap management.
    • Access to non-local data.
    • Handling of procedures/functions and activation records.

Parsing Techniques

  • Parsing techniques are used to analyze the syntax structure of a program (often using context-free grammars).
  • Two main types of parsing methods:
    • Top-down parsing.
    • Bottom-up parsing.
  • An LR parser performs error recovery by skipping some input tokens or making a change in the state/stack to continue parsing.

Error Handling

  • Handling errors in every phase (lexical, syntax, semantic, etc).
  • Reporting the reason and position of the error.

Code Optimization

  • Techniques for improving the performance of generated code.
  • Peephole optimization and other global optimizations.

Data Flow Analysis

  • An analysis of how data flows through a program.
  • Aims to determine which variables are live and available at different points in the code.
  • Helps to perform optimizations, such as common subexpression elimination, by enabling the compiler to track the progress of data between instructions.

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Compiler Design (57 Pages) PDF

Description

Test your knowledge on Type-1 grammars, lexical analysis, and the compilation process. This quiz covers the different types of grammars, their characteristics, and how they are applied in language recognition. Challenge yourself with questions about production forms and their significance in computer science.

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