lecture 1

Question 1

What are the major compiler phases?

Answer 1

Lexical Analysis (Scanning) – breaks source code into tokens.

Syntactic Analysis (Parsing) – constructs a parse tree from tokens.

Semantic Analysis – checks for type errors, undeclared variables, etc.

Intermediate Code Generation – produces platform-independent code.

Optimization – improves code performance or size.

Target Code Generation – translates intermediate code into assembly/machine code.

Question 2

What is the difference between the analysis and synthesis phases?

Answer 2

Analysis phase: Converts source code into an internal representation.

Synthesis phase: Converts the internal representation into target code.

Question 3

Why do we use intermediate code?

Answer 3

It allows for:

Easier optimization.

Reuse of the front-end for multiple target platforms.

Reuse of the back-end for multiple source languages.

Question 4

What is the advantage of separating the front and back ends?

Answer 4

Promotes modularity and reuse:

Front-end (e.g., parsing, semantics): source language-specific.

Back-end (e.g., code generation): target machine-specific.

Question 5

What is a lexeme?

Answer 5

A sequence of characters in the source code that matches the pattern for a token.

Question 6

What is a token?

Answer 6

A symbolic representation of a lexeme, possibly with attributes (e.g., ID(“x”)).

Question 7

What is a parse tree?

Answer 7

A tree that represents the entire grammar structure of the input source code, including all syntactic rules and tokens.

Question 8

What is an abstract syntax tree (AST)?

Answer 8

A simplified version of the parse tree:

Removes unnecessary grammar rules and tokens.

Focuses only on the meaningful structure of the code.

Question 9

What is intermediate code?

Answer 9

Independent of source and target language.

Question 10

What is the difference between assembly code, object code, and executable code?

Answer 10

Assembly code: Human-readable instructions for a specific CPU.

Object code: Machine-readable code, output by the assembler, with placeholders for addresses (not executable yet).

Executable code: Final code after linking, with all addresses resolved.

Question 11

What is bytecode, an interpreter

Answer 11

Bytecode: Platform-independent low-level code (e.g., Java bytecode).

Interpreter: Executes code directly without compiling to machine code.