Compiler Design - Lecture Notes

Introduction to Compiler

What is a Compiler?

• A compiler is a software that converts a program written in a High Level Language (HLL) to a Low Level Language (LLL).
• Source language (HLL): For example, Java, C programs written using English alphabets.
• Target language (LLL): Assembly language or machine level language that the system can understand.

Role of the Compiler

• Converts high level language to low level language for system processing.
• Example process: Java/C high level code -> Low level language -> Machine code.

Language Processing System

Stages of Language Processing

1. Source Code (High Level Language)
2. Preprocessor
   • Removes include directives (e.g., #include, #define in C).
   • Performs file inclusions, augmentations, and macro processing.
3. Compiler
   • Translates the program from high level language to assembly language (low level language).
4. Assembler
   • Translates assembly language (low level) to machine language (object code).
5. Loader/Linker
   • Loads and links all parts of the program together for execution.
   • Generates relocatable machine code which can be loaded and run at any point in memory.

Detailed Steps

• Preprocessor: Removes directives like #include, #define and replaces them with appropriate code inclusions.
• Compiler (focus): Converts high level language code to low level language (mnemonics like ADD, MOV).
• Assembler: Converts low level language to machine code (binary numbers).
• Loader/Linker: Links library functions and loads the machine code into memory for execution.

Example: C Program Compilation

• Writing a C program using high level language.
• C Compiler: Converts high level language to low level language (assembly).
• Assembler: Converts low level assembly language to machine code (object code).
• Linker: Links all parts of the program together including necessary library functions.
• Loader: Loads all linked parts into memory and executes the program.

Key Points

• Compiler: High Level Language to Low Level Language (Assembly).
• Assembler: Low Level Language to Machine Language (Binary code).
• Statements are converted to mnemonics, and mnemonics are converted to binary numbers (machine code).

Focus on Compiler

• Compiler's Role: Convert high level language to assembly language.
• Internal Process: Understand statements into mnemonics conversion and mnemonics into binary code.

Summary

• High Level Language (Source Code)
• Compiler -> Low Level Language (Assembly, mnemonics)
• Assembler -> Machine Language (Binary)
• Linker/Loader -> Executes program in memory.

Thank you.