Compiler Construction

A compiler front-end implemented in C for a custom programming language, supporting lexical analysis, grammar-based parsing, token generation, and syntax validation.

This project was developed as part of a compiler construction course and focuses on building core components of a language-processing pipeline from scratch.

---

Features

• Lexical analysis for tokenizing source code
• Comment removal utility
• Token list generation with line numbers
• Grammar-based parsing using FIRST and FOLLOW sets
• Predictive parsing using parse table construction
• Syntax checking for input source programs
• CPU time measurement for lexer and parser execution

---

Project Structure

• driver.c – Menu-driven entry point for running compiler functionalities
• lexer.c, lexer.h, lexerDef.h – Lexical analyzer implementation
• parser.c, parser.h, parserDef.h – Parser implementation
• Grammar.txt – Grammar specification
• First.txt – FIRST sets
• Follow.txt – FOLLOW sets
• NTerminals.txt – Non-terminal definitions
• tokenId.txt – Token mapping/reference
• t1.txt to t6.txt – Sample test cases
• makefile – Build instructions

---

Build

Compile the project using:

make

This generates the executable:

stage1exe

---

Run

Run the compiler front-end with:

./stage1exe <input_file> <output_file>

Example:

./stage1exe t1.txt output.txt

---

Menu Options

After running the executable, choose from:

• 0 – Exit
• 1 – Remove comments and print cleaned code
• 2 – Print token list
• 3 – Check syntactic correctness of the input source code
• 4 – Print total time taken by lexer and parser

---

Concepts Implemented

• DFA-based lexical analysis
• Token recognition and symbol handling
• Grammar representation
• FIRST and FOLLOW set computation
• Predictive (LL) parsing
• Parse table construction
• Syntax validation

---

Sample Output

The program can:

• Print lexemes and token names with line numbers
• Validate syntactic correctness of input programs
• Generate parser-related output files

---

Notes

• This project focuses on compiler front-end design (lexing + parsing), not code generation
• Grammar and parsing data are loaded from external text files
• Sample test inputs are included in the repository

---

Acknowledgment

Developed collaboratively as part of a compiler construction course at BITS Pilani.