📟 Smart ATM Simulator (C Project)

A console-based ATM Simulator built in C, designed to replicate essential banking operations such as secure PIN verification, withdrawals, deposits, balance enquiry, PIN change, and basic transaction history.

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📘 1. Project Overview

The project demonstrates how an ATM operates at a logical level using structured programming in C.

🔹 Secure 4-digit PIN authentication
🔹 Modular code structure
🔹 Console-based UI
🔹 Basic transaction logging
🔹 Clean and simple workflow

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🧩 2. Features

🔐 User Functions

✔️ 4-digit PIN authentication
✔️ Masked PIN input (****)
✔️ Withdraw (with balance validation)
✔️ Deposit
✔️ Balance enquiry
✔️ Transaction summary
✔️ Change PIN
✔️ Exit session safely

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🧠 3. System Design

🔹 Logical Components

• 🧾 User Data Handling: struct-based account storage
• 🔐 Authentication Module: masked PIN + validation
• 💸 Transaction Processing: withdraw/deposit logic
• 📋 Menu Handling: clean switch-case based flow
• 🔑 PIN Management: secure PIN update

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🛠️ 4. Technical Details

🖥️ Language and Tools

• 🔹 C Programming
• 🔹 GCC Compiler
• 🔹 Code::Blocks / VS Code

💡 Concepts Used

• 📌 Structures (struct)
• 📌 Functions (modular approach)
• 📌 Loops & condition checks
• 📌 Input handling
• 📌 Optional: <conio.h>, <time.h>, <windows.h>

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🖥️ 5. Sample Output

🔵 Login & Menu

=== Smart ATM Simulator === Insert Card... Enter 4-digit PIN: **** Login successful.

1. Withdraw
2. Deposit
3. Balance Enquiry
4. Transaction Summary
5. Change PIN
6. Exit

🧾 Transaction Summary

Recent Transactions:

• Withdraw: Rs. 400.00
• Deposit: Rs. 100.00
• Withdraw: Rs. 300.00

🟩 Deposit Example

Enter amount to deposit: 500 Amount deposited successfully.

📊 Balance Enquiry

Your current balance is: Rs. 3040.00

🔐 PIN Change

Enter old PIN: **** Enter new PIN: **** PIN changed successfully.

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📁 6. Project Structure

│atm-simulation-system/
│
├── README.md
│
├── src/
│   └── main_code.c   ✅ (FULL CODE HERE)
│
├── docs/
│   ├── PROJECT_OVERVIEW.md
│   ├── ALGORITHM.md
│   ├── STATE_MACHINE.md
│   ├── SETUP_GUIDE.md
│   ├── TEST_RESULTS.md
│   ├── KNOWN_LIMITATIONS.md
│   └── LEARNING_OUTCOMES.md
│
├── data/
│   ├── history_1001.txt
│   └── history_1002.txt
│
├── ide/
│   ├── ATM.cbp
│   ├── ATM.layout
│   └── ATM.depend
│
└── build/
    ├── main.exe
    └── main_code.o

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