🔧 Mini Compiler using Flex & Bison

A lightweight **Mini Compiler** built using **Flex (Lex)**, **Bison (YACC)**, and **C**. The project demonstrates the fundamental phases of compiler construction, including lexical analysis, syntax analysis, parsing, symbol table generation, and intermediate instruction generation.

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🚀 Features

• ✅ Lexical Analysis using Flex
• ✅ Syntax Analysis using Bison
• ✅ Token Recognition
• ✅ Parsing and Grammar Validation
• ✅ Symbol Table Generation
• ✅ Intermediate Instruction Generation
• ✅ Error Detection and Reporting
• ✅ Command-Line Based Compiler Workflow

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🏗 Compiler Architecture

Source Code
     │
     ▼
Lexical Analyzer (Flex)
     │
     ▼
Token Stream
     │
     ▼
Parser (Bison)
     │
     ▼
Syntax Tree / Validation
     │
     ▼
Symbol Table Generation
     │
     ▼
Intermediate Instructions

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🛠 Technologies Used

Technology	Purpose
C	Core Implementation
Flex (Lex)	Lexical Analysis
Bison (YACC)	Syntax Analysis & Parsing
GCC	Compilation
Ubuntu 24.04	Development Environment
Oracle VirtualBox	Virtualized Environment
Git & GitHub	Version Control

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📂 Project Structure

mini_compiler/
│
├── lexer.l
├── parser.y
├── input.txt
├── input2.txt
├── compiler
├── README.md
├── LICENSE
└── .gitignore

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⚙️ Installation

Install Required Packages

sudo apt update
sudo apt install flex bison gcc make git -y

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🔨 Build Instructions

Generate lexer and parser files:

flex lexer.l
bison -d parser.y

Compile the compiler:

gcc lex.yy.c parser.tab.c -o compiler -lfl

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▶️ Running the Compiler

Test Input 1

./compiler < input.txt

Test Input 2

./compiler < input2.txt

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🧪 Sample Source Code

int a;

a = 10;

if (a > 5) {

    int b;
    b = a + 2;

    while (b > 0) {

        int c;
        c = b - 1;

        b = b - 1;
    }
}

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📚 Supported Language Elements

Category	Supported Elements
Data Types	int, float
Conditional Statements	if, else
Loops	while
Arithmetic Operators	+, -, *, /
Relational Operators	==, !=, <, >, <=, >=
Delimiters	;
Brackets	(), {}
Variable Declarations	Supported
Assignments	Supported

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📈 Learning Outcomes

Through this project, the following compiler design concepts were explored:

• Compiler Construction Fundamentals
• Lexical Analysis
• Syntax Analysis
• Parsing Techniques
• Context-Free Grammars
• Symbol Table Management
• Intermediate Code Representation
• Flex & Bison Integration
• Linux-Based Development Workflow

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🎓 Academic Relevance

This project was developed as part of Compiler Design coursework and serves as a practical demonstration of how programming language source code is analyzed and processed during compilation.

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🔮 Future Improvements

• Semantic Analysis
• Abstract Syntax Tree (AST) Generation
• Type Checking
• Optimization Passes
• Three-Address Code Generation
• Assembly Code Generation
• Enhanced Error Recovery

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👨‍💻 Author

Md Tausif Uddin

Department of Computer Science & Engineering (CSE)
University of Asia Pacific (UAP)

GitHub: https://github.com/tausif112

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📜 License

This project is licensed under the MIT License.