A12: Token Builder

Create Your Own ERC-20 Token

Overview

In this hands-on assignment you will build and deploy your own ERC-20 token using the Solidity programming language and the Remix IDE. You will start from a starter template, fill in the missing functions, deploy the token, and then extend it with a custom feature such as burning, minting, or pausing. Finally, your group will present the token to the class.

Prerequisites

• Lesson 10 (Solidity Basics) -- data types, functions, mappings, constructors, events
• Basic understanding of ERC-20 token standard (covered in Lessons 7 and 10)
• A modern web browser (Chrome, Firefox, or Edge)

Activity Structure

1 Setup and Starter Code (5 minutes)

• Open remix.ethereum.org in your browser
• Create a new file called MyToken.sol
• Copy the starter code from the Starter Code page into your file
• Read through the TODO comments to understand what you need to implement

2 Build the Base Token (25 minutes)

Complete the following functions in the starter code. Each has a TODO comment explaining what to implement:

1. Constructor: Set the token name, symbol, decimals (18), and initial supply. Assign all tokens to msg.sender
2. transfer(): Move tokens from the caller to another address. Use require() to check the sender has enough tokens. Emit a Transfer event
3. approve(): Allow a spender to withdraw from the caller's account up to a specified amount. Emit an Approval event
4. transferFrom(): Move tokens on behalf of another user (if approved). Check both balance and allowance. Update the allowance after transfer

3 Deploy and Test (10 minutes)

1. In Remix, go to the Deploy & Run Transactions panel (left sidebar)
2. Make sure Environment is set to "Remix VM (Shanghai)" or "Remix VM (Cancun)"
3. Enter your initial supply in the constructor argument (e.g., 1000000)
4. Click Deploy
5. Test your contract:
   • Call balanceOf with your address -- should show total supply
   • Call transfer to send tokens to a second test account
   • Call approve then transferFrom from a different account
   • Verify balances update correctly after each operation

4 Add a Custom Feature (15 minutes)

Choose at least one of the following features to add to your token:

5 Presentation (5 minutes total -- 2 min/group)

Prepare a short presentation for the class covering:

• Token Identity: What did you name your token? What is the symbol?
• Feature Demo: Show your custom feature working in Remix (live or screenshot)
• Design Decision: Why did you choose this feature? What real-world token uses it?
• Challenge: What was the hardest part of the implementation?

Deliverables

Tips for Success

• Start with the starter code: Do not write from scratch. The template has the structure ready -- just fill in the TODO sections
• Compile after every function: Fix errors incrementally. Solidity error messages are specific and helpful
• Test with small numbers: Use an initial supply of 1000 or 10000, not billions. It makes debugging easier
• Use multiple accounts: Remix provides 15 test accounts. Use at least 2 to test transfers
• Read the error messages: If require() fails, Remix shows the error string you provided
• Check the Lesson 10 slides: Every function you need to write was demonstrated step by step

Submission Instructions

1. Keep your Remix IDE open with the deployed contract visible
2. Write a short reflection (3-5 sentences) on what you learned and what you found challenging. Include this in your presentation or submit as a separate note
3. Be prepared to demonstrate your contract live to the instructor if asked
4. All group members should be able to explain every function in the contract