GATE CS 1987 Q1-xi — Lexical Analysis

The correct option is C.

Here is a breakdown of the roles of the compiler phases mentioned:

• Lexical Analyser (Scanner): This is the first phase of a compiler. It reads the source program character-by-character, groups these characters into meaningful sequences called lexemes, and translates them into a stream of tokens. Thus, it is the module that inspects every single character of the source text.
• Syntax Analyser (Parser): This phase takes the stream of tokens produced by the lexical analyser and groups them into grammatical phrases, represented by a parse tree. It operates on tokens, not individual characters.
• Code Optimiser: This phase attempts to improve the intermediate code so that the resulting target program runs faster or consumes less memory.
• Code Generator: This phase maps the intermediate representation of the source program into the target language (usually machine code or assembly language).