Phases of Compiler

Introduction

• Overview of the compiler design and its structure.
• Previous discussion on language processing systems, converting high-level language to low-level language (assembly/machine code).

Compiler Phases

• Definition of a Phase:
  • A phase is a logically interrelated operation that takes a source program in one representation and produces output in another representation.
  • Each phase takes input and gives output to the next phase.

Major Phases of Compilation

• Total compilation is divided into two major phases:
  1. Analysis Phase
  2. Synthesis Phase

Analysis Phase

• Characteristics:
  • Machine independent.
  • Language dependent.
• Focuses on the source language.

Synthesis Phase

• Characteristics:
  • Machine dependent.
  • Language independent.
• Focuses on the machine language (low-level language).

Structure of the Compiler

1. Source Program: High-level language code.
2. Target Program: Low-level language code (after compilation).
3. Phases of Compilation:
   • Lexical Analyzer
   • Syntax Analyzer
   • Semantic Analyzer
   • Intermediate Code Generator
   • Code Optimizer
   • Code Generator
4. Symbol Table Manager:
   • Stores symbol-related information.
   • Handles errors that may occur during any phase.

Detailed Explanation of the First Phase: Lexical Analysis

• Function:
  • Reads a stream of characters from the source program.
  • Groups characters into meaningful sequences called lexemes.
• Representation:
  • Lexical Analyzer represents lexemes as tokens.

Example of Lexical Analysis

• Example Statement: new_value = old_value + 12
  • Tokens generated:
    • new_value -> Identifier
    • = -> Assignment Operator
    • old_value -> Identifier
    • + -> Add Operator
    • 12 -> Number
• Additional Operations:
  • Removes white spaces and identifies errors.

Conclusion

• The first phase of the compiler, Lexical Analysis, has been discussed.
• Further phases will be explained in the next session.