Clear DefinitionsToken Contract
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Pronunciation
[toh-ken kon-trakt]
Analogy
A token contract is like a bank’s ledger system—it keeps track of account balances and enforces transfer rules.
Definition
A smart contract implementing a digital asset standard (e.g., ERC‑20, ERC‑721) that defines token issuance, transfer, and metadata.
Key Points Intro
Token contracts provide asset functionality via:
Key Points
Balance mapping: `mapping(address=>uint256)` for fungible tokens.
Transfer functions: `transfer`, `transferFrom`, `approve`.
Events: `Transfer`, `Approval` for off‑chain indexing.
Metadata: Name, symbol, decimals fields.
Example
An ERC‑20 token contract includes `function transfer(address to, uint256 amt) external returns (bool)` and emits `Transfer(msg.sender, to, amt)`.
Technical Deep Dive
ERC‑20 defines a standard interface: `totalSupply()`, `balanceOf()`, `transfer()`, `approve()`, `transferFrom()`, `allowance()`. Contracts maintain `balances` and `allowances` mappings. They use `SafeMath` for arithmetic and emit events for each operation. Metadata functions are optional but widely adopted.
Security Warning
Beware of the ERC‑20 approval race condition; use `increaseAllowance`/`decreaseAllowance` patterns.
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