UNIVERSITY OF WEST ATTICA
SCHOOL OF ENGINEERING
DEPARTMENT OF COMPUTER ENGINEERING AND INFORMATICS

University of West Attica · Department of Computer Engineering and Informatics

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Compilers

Design and Implementation of a Compiler at Uni-C

Vasileios Evangelos Athanasiou
Student ID: 19390005

GitHub · LinkedIn

Georgios Theocharis
Student ID: 19390283

GitHub

Ioannis Iliou
Student ID: 19390066

GitHub · LinkedIn

Pantelis Tatsis
Student ID: 20390226

GitHub · LinkedIn

Vasileios Dominaris
Student ID: 21390055

GitHub

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Supervision

Supervisor: Christos Troussas, Assistant Professor

UNIWA Profile · LinkedIn

Co-supervisor: Michalis Iordanakis, Academic Scholar

UNIWA Profile · Scholar

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Athens, May 2024

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README

Design and Implementation of a Compiler at Uni-C

This project involves the development of a compiler for Uni-C, a subset of the C programming language. The implementation was completed in three distinct phases, covering the fundamental stages of compiler construction:

1. Finite State Machine (FSM) Encoding
   Design and simulation of automata for recognizing lexical units.

2. Lexical Analysis (FLEX)
   Development of a lexical analyzer that identifies tokens using regular expressions.

3. Syntactic Analysis (BISON)
   Construction of a parser that validates program structure based on predefined grammar rules.

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Table of Contents

Section	Folder	Description
1	A-FLEX/	Lexical analysis phase using Finite State Machines and FLEX
1.1	A-FLEX/A2-FSM/	FSM design and implementation for Uni-C tokens
1.1.1	A-FLEX/A2-FSM/docs/	FSM theory notes, transition tables, and documentation (PDF/XLSX)
1.1.2	A-FLEX/A2-FSM/src/	FSM source files for identifiers, strings, numbers, comments, and whitespace
1.2	A-FLEX/A3-FLEX/	FLEX-based lexical analyzer implementation
1.2.1	A-FLEX/A3-FLEX/docs/	FLEX code documentation
1.2.2	A-FLEX/A3-FLEX/src/	FLEX source code, Makefile, input/output samples
1.3	A-FLEX/assign/	Assignment descriptions for Part A (FSM & FLEX)
2	B-BISON/	Syntax analysis phase using BISON
2.1	B-BISON/assign/	Assignment descriptions for Part B (BISON)
2.2	B-BISON/B2-FLEX-BISON/	Combined FLEX & BISON parser implementation
2.2.1	B-BISON/B2-FLEX-BISON/src/	Integrated lexer/parser source code and build files
2.3	B-BISON/B3-COMPILER/	Final compiler stage
2.3.1	B-BISON/B3-COMPILER/docs/	BISON grammar documentation
2.3.2	B-BISON/B3-COMPILER/src/	Final Uni-C compiler source code
3	Uni-C/	Language specification and usage guide for Uni-C
4	README.md	Project documentation
5	INSTALL.md	Usage instructions

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1. Lexical Analysis (Tokens)

The compiler recognizes the following categories of tokens:

• Identifiers
  Names for variables and functions

  • Pattern: [a-zA-Z_][a-zA-Z0-9_]{0,31}

• Keywords
  Reserved words such as:

  • if, else, while, int, return, func

• Constants
  Supported constant types include:

  • Integers (decimal, octal, hexadecimal)
  • Floating-point numbers
  • Strings

• Operators

  • Arithmetic: +, -, *, /
  • Relational: >, <, ==
  • Logical: &&, ||

• Delimiters

  • Characters such as ; used to separate commands

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2. Finite State Machine (FSM)

For each token category, a Finite State Automaton (FSA) was designed.

Example – Identifiers:

• Starts at an initial state (SZ)
• Transitions to a middle-character state (SMCH) upon receiving a letter or underscore
• Reaches a GOOD exit state upon encountering a newline, provided the identifier is valid

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3. Syntactic Analysis (BISON)

The BISON parser generator is used to define and enforce grammar rules for Uni-C programs:

• Variable Declarations

  • Support for simple data types and arrays

• Functions

  • Recognition of both built-in and user-defined functions

• Expressions

  • Handling of simple and compound expressions

• Error Handling

  • Detection and reporting of syntax errors
  • Handling of invalid tokens (TOKEN ERROR)

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4. Project Files

• 1_identifiers.fsm
  FSM encoding for identifier recognition

• simple-flex-code.l
  FLEX source file containing regular expressions and token definitions

• token.h
  Header file defining numeric constants for tokens

• simple-bison-code.y
  BISON source file containing grammar and syntax rules