Hands-On Guide to Creating Your Own Cryptocurrency: ERC-20 Token Functions Explained

Understanding ERC-20 Token Functions

From the previous chapter, you now have your own cryptocurrency wallet. The next step is to start coding your cryptocurrency. Below, we'll break down the essential API functions of the ERC-20 standard using the EIP20Interface.sol template. These functions define the core operations of any ERC-20 token.

Core Functions of ERC-20 Tokens

1. function transfer(address _to, uint256 _value) public returns (bool success);

   • Transfers tokens to another account.
   • _value: Amount of tokens to transfer.
   • _to: Recipient's address.
   • Uses require(balances[msg.sender] >= _value); to verify the sender has sufficient balance.

2. function transferFrom(address _from, address _to, uint256 _value) public returns (bool success);

   • Allows a third-party app to transfer tokens on your behalf.
   • _value: Transfer amount.
   • _to: Recipient address.
   • _from: Source address.
   • Uses uint256 allowance = allowed[_from][msg.sender] and require(balances[_from] >= _value && allowance >= _value) to validate permissions and balances.

3. function balanceOf(address _owner) public view returns (uint256 balance);

   • Returns the token balance of _owner.

4. function approve(address _spender, uint256 _value) public returns (bool success);

   • Authorizes _spender to withdraw tokens up to _value.

5. function allowance(address _owner, address _spender) public view returns (uint256 remaining);

   • Checks remaining tokens _spender can transfer from _owner.

Frequently Asked Questions (FAQs)

1. What is the ERC-20 standard?

ERC-20 is a technical standard for fungible tokens on Ethereum, ensuring interoperability across wallets and exchanges.

2. Why use transferFrom instead of transfer?

👉 Discover the power of decentralized finance with transferFrom, which enables delegated transactions (e.g., for dApps or exchanges).

3. Can I change the approved amount after calling approve?

Yes, you can update it by calling approve again with a new value.

4. How do I check my token balance?

Use balanceOf(yourAddress) to query your balance anytime.

Key Takeaways

• ERC-20 tokens rely on 5 critical functions for transfers, approvals, and balance checks.
• Always verify balances and allowances to prevent failed transactions.
• Use approve cautiously to limit third-party access.

Ready to dive deeper? The next chapter covers variables and events in EIP20.sol. Stay tuned!

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6. DeFi basics  
7. Solidity programming