📒 Address Book — C Console Application

Your contacts, organized and persistent. A console-based Address Book written in C with full CRUD operations, smart sorting, input validation, and automatic file storage — all from the terminal.

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✨ Features

Feature	Description
➕ Create	Add contacts with name, phone number, and email
🔍 Search	Find contacts instantly by name
✏️ Edit	Update any detail of an existing contact
🗑️ Delete	Remove contacts cleanly from the address book
📋 List & Sort	View all contacts — sort by Name, Phone, or Email
💾 Persistent Storage	Contacts auto-saved to contacts.txt across sessions
✅ Input Validation	Duplicate phone/email detection, name format checks

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🗂️ Project Structure

AddressBook/
├── 📄 main.c          # Entry point — menu-driven interface
├── 📄 contact.c       # Core CRUD operations (create, search, edit, delete, list)
├── 📄 contact.h       # Structs and function declarations
├── 📄 file.c          # File handling — save and load contacts
├── 📄 file.h          # File function declarations
├── 📄 validation.c    # Input validation (name, phone, email)
├── 📄 populate.c      # Helper to pre-populate sample contacts
├── 📄 populate.h      # Populate function declaration
└── 📁 contacts.txt    # Persistent contact storage (auto-generated)

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🚀 Getting Started

🛠️ Prerequisites

• GCC compiler
• Linux / Unix environment (or WSL on Windows)

🔧 Build & Run

# Clone the repository
git clone https://github.com/<your-username>/AddressBook.git
cd AddressBook

# Compile
gcc main.c contact.c file.c validation.c populate.c -o addressbook

# Run
./addressbook

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📖 Usage

Once launched, you'll see an interactive menu:

+----------------------------------+
|         ADDRESS BOOK MENU        |
+----------------------------------+
| 1. Create contact                |
| 2. Search contact                |
| 3. Edit contact                  |
| 4. Delete contact                |
| 5. List all contacts             |
| 6. Save contacts                 |
+----------------------------------+

➕ Creating a Contact

Enter a name, phone number, and email. The app checks for:

• 🚫 Duplicate phone numbers
• 🚫 Duplicate email addresses
• 🚫 Invalid name formats (numbers, special characters)

📋 Listing & Sorting Contacts

When listing contacts, choose your preferred sort order:

Option	Sort By
1	🔤 Name (A → Z)
2	📞 Phone Number
3	📧 Email Address
4	🕐 Normal (insertion order)

💾 Persistent Storage

All contacts are saved to contacts.txt automatically. On the next launch, your address book is restored exactly as you left it — no data loss between sessions.

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✅ Input Validation Rules

Field	Validation
👤 Name	Alphabets and spaces only; no numbers or symbols
📞 Phone	Numeric only; no duplicate entries allowed
📧 Email	Must follow [email protected] format; no duplicates

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🧠 Concepts Used

Concept	Role in Project
🧱 Structures	Contact struct to bundle name, phone, and email
📁 File Handling	Read/write contacts to contacts.txt for persistence
🔡 String Manipulation	Search, compare, format, and validate contact fields
🧩 Modular Programming	Logic split across contact.c, file.c, validation.c
📐 Dynamic Arrays	Manage a growing list of contacts at runtime
✅ Input Validation	Prevent duplicates and enforce field format rules

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🛠️ Technologies Used

• Language: C
• Compiler: GCC
• Platform: Linux / Unix / WSL

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👤 Author

Amar C M 🔧 Embedded Systems Engineer

📧 [email protected]

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📜 License

This project is open-source and available under the MIT License.

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💡 "Good code is organized code — and so are good contacts."