Added links to all codes in readme file.

Codes/Code-1.md

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+# Practical-1: MetaMask Installation and Ether Spending Study
+
+## Step 1: Install MetaMask
+
+### For Desktop (Browser)
+
+1. Open your preferred browser (Chrome, Firefox, Edge, or Brave).
+2. Go to the official MetaMask website: [https://metamask.io](https://metamask.io)
+3. Click **"Download"** and select your browser.
+4. Add the extension to your browser.
+5. Open MetaMask, and follow the setup:
+   - **Create a new wallet** or **import an existing one**.
+   - Set a **strong password**.
+   - **Backup your secret recovery phrase** securely.
+
+### For Mobile
+
+1. Go to your App Store (iOS) or Google Play Store (Android).
+2. Search for **MetaMask**.
+3. Download and install the app.
+4. Follow similar setup steps (create wallet, backup phrase).
+
+## Step 2: Connect MetaMask to a Network
+
+- By default, MetaMask uses the **Ethereum Mainnet**.
+- To use test networks for learning, click the network dropdown and select a testnet like **Goerli Test Network**.
+- Obtain free test Ether from a Goerli faucet: [https://goerlifaucet.com/](https://goerlifaucet.com/).
+
+## Step 3: Understanding Ether Spending per Transaction
+
+### Key Concepts
+1. **Gas Limit:** Maximum units of gas you are willing to spend.
+2. **Gas Price:** Price per gas unit in **Gwei** (1 ETH = 1,000,000,000 Gwei).
+3. **Transaction Fee = Gas Limit × Gas Price**
+
+## Step 4: Make a Test Transaction
+
+1. Ensure your wallet has ETH (test ETH on testnets).
+2. Click **Send** in MetaMask.
+3. Enter the recipient address and amount.
+4. Adjust **Gas Fee** if desired.
+5. Confirm the transaction.
+
+## Step 5: Observe Spending
+
+- After sending, MetaMask displays the **Transaction Fee** in ETH.
+- To see detailed info, check **Etherscan**:
+  1. Copy the transaction hash from MetaMask.
+  2. Go to [https://etherscan.io](https://etherscan.io) or testnet explorer like [https://goerli.etherscan.io](https://goerli.etherscan.io).
+  3. Paste the hash to see gas used and ETH spent.
+
+## Step 6: Experiment
+
+- Send multiple transactions with different **gas prices**.
+- Observe how fees change based on **network congestion**.
+- Try interacting with **smart contracts** to see higher gas usage.
+
+## Tips
+- Always use a testnet first to avoid losing real ETH.
+- MetaMask provides detailed transaction history and gas usage.
+

Codes/Code-2.md

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+# Practical-2: How to Create Your Own Wallet Using MetaMask for Crypto Transactions
+
+MetaMask is a popular cryptocurrency wallet that allows you to manage Ethereum-based assets and interact with decentralized applications (dApps). Follow the steps below to create your own wallet.
+
+---
+
+## Step 1: Install MetaMask
+
+1. Go to the official MetaMask website: [https://metamask.io](https://metamask.io)
+2. Click on **"Download"**.
+3. Choose your platform:
+   - **Browser Extension**: Chrome, Firefox, Brave, Edge
+   - **Mobile App**: iOS or Android
+4. Install the extension or app.
+
+---
+
+## Step 2: Create a New Wallet
+
+1. Open MetaMask.
+2. Click on **"Get Started"**.
+3. Select **"Create a Wallet"**.
+4. Set a **strong password** for local access. This password is used to unlock your wallet on your device.
+5. Click **"Create"**.
+
+---
+
+## Step 3: Backup Your Secret Recovery Phrase
+
+1. MetaMask will display a **12-word Secret Recovery Phrase**. This is extremely important.
+2. Write it down on paper and **store it securely**.  
+   ⚠️ **Never share your recovery phrase with anyone.**
+3. Confirm the recovery phrase by selecting the words in order.
+4. Click **"Confirm"**.
+
+---
+
+## Step 4: Access Your Wallet
+
+1. Once confirmed, your wallet is ready.
+2. You can view your wallet address by clicking on **Account 1** at the top.
+3. This address can be shared to **receive crypto**.
+
+---
+
+## Step 5: Add Funds to Your Wallet
+
+1. Buy crypto from an exchange (like Coinbase, Binance, or WazirX).
+2. Transfer it to your MetaMask wallet address.
+3. Wait for the transaction to be confirmed.
+
+---
+
+## Step 6: Use Your Wallet for Transactions
+
+- **Send crypto:** Click **Send**, enter the recipient’s address and amount.
+- **Receive crypto:** Share your wallet address.
+- **Interact with dApps:** Connect MetaMask to decentralized applications by clicking **Connect Wallet** on supported websites.
+
+---
+
+## Step 7: Security Tips
+
+- **Never share your password or Secret Recovery Phrase.**
+- Enable **two-factor authentication (2FA)** on exchange accounts.
+- Keep MetaMask updated to the latest version.
+- Consider using **hardware wallets** for storing large amounts of crypto.
+
+---
+
+## References
+
+- [MetaMask Official Website](https://metamask.io)
+- [MetaMask User Guide](https://metamask.zendesk.com/hc/en-us)

Codes/Code-3.sol

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+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.20;
+
+contract BankAccount {
+    mapping(address => uint256) private balances;
+
+    event Deposit(address indexed account, uint256 amount);
+    event Withdraw(address indexed account, uint256 amount);
+
+    function deposit() public payable {
+        require(msg.value > 0, "Deposit amount must be greater than 0");
+        balances[msg.sender] += msg.value;
+        emit Deposit(msg.sender, msg.value);
+    }
+
+    function withdraw(uint256 amount) public {
+        require(amount > 0, "Withdraw amount must be greater than 0");
+        require(balances[msg.sender] >= amount, "Insufficient balance");
+
+        balances[msg.sender] -= amount;
+        payable(msg.sender).transfer(amount);
+
+        emit Withdraw(msg.sender, amount);
+    }
+
+    function getBalance() public view returns (uint256) {
+        return balances[msg.sender];
+    }
+}

Codes/Code-4.sol

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+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.20;
+
+contract StudentData {
+    struct Student {
+        uint256 id;
+        string name;
+        uint8 age;
+        string course;
+    }
+
+    Student[] private students;
+
+    event StudentAdded(uint256 id, string name, string course);
+    event FallbackCalled(address sender, uint value, string message);
+
+    function addStudent(uint256 _id, string memory _name, uint8 _age, string memory _course) public {
+        students.push(Student(_id, _name, _age, _course));
+        emit StudentAdded(_id, _name, _course);
+    }
+
+    function getStudent(uint256 index) public view returns (uint256, string memory, uint8, string memory) {
+        require(index < students.length, "Invalid index");
+        Student memory s = students[index];
+        return (s.id, s.name, s.age, s.course);
+    }
+
+    function getTotalStudents() public view returns (uint256) {
+        return students.length;
+    }
+
+    fallback() external payable {
+        emit FallbackCalled(msg.sender, msg.value, "Fallback function triggered!");
+    }
+
+    receive() external payable {
+        emit FallbackCalled(msg.sender, msg.value, "Receive function triggered!");
+    }
+}

README.md

@@ -6,6 +6,13 @@ This repository contains comprehensive resources for the Blockchain Technology c
 
 ## Index
 
+### Codes
+
+1. [Code-1 (MetaMask Installation)](Codes/Code-1.md)
+2. [Code-2 (MetaMask Account Creation)](Codes/Code-2.md)
+3. [Code-3 (Bank Account)](Codes/Code-3.sol)
+4. [Code-4 (Student Data)](Codes/Code-4.sol)
+
 ### Notes
 
 1. [Unit 1 - Mathematical Foundation for Blockchain](Notes/Unit%201%20-%20Mathematical%20Foundation%20for%20Blockchain)