In the compilation of a PL/I (or similar) program, what does the Lexical Analysis phase primarily accomplish?

Introduction / Context:
Compilers transform high-level source code into executable form through a pipeline of phases. The first substantive phase after preprocessing is lexical analysis (scanning), which converts raw character streams into tokens for the parser.

Given Data / Assumptions:

• Source language is PL/I or a similar high-level language.
• We distinguish between lexing (tokens) and parsing (syntactic structures).
• Uniform symbols (tokens) are the standardized representation of basic language elements.

Concept / Approach:

Lexical analysis groups characters into meaningful units: identifiers, keywords, literals, operators, delimiters. It may also remove whitespace/comments and normalize representations (e.g., number formats). The output is a token stream, often with symbol table entries for identifiers and literals, which feeds the parser for grammar-based analysis.

Step-by-Step Solution:

Verification / Alternative check:

Standard compiler design references separate scanner and parser phases exactly along these lines.

Why Other Options Are Wrong:

• syntactic reductions: parser activity.
• optimal matrix / macro processor: optimization and macro expansion are separate concerns.

Common Pitfalls:

• Mistaking symbol table construction as purely lexical; parser and semantic phases also contribute entries—lexing focuses on tokens.

Final Answer:

recognition of basic elements and creation of uniform symbols.