Blockchain tokens existed before Ethereum.
- In some ways, the blockchain currency, Bitcoin, may betoken itself.
- There are many token platforms that were also developed on Bitcoin and other cryptocurrencies before Ethereum.
- The introduction of the first token standard on Ethereum led to an explosion of tokens.
Tokens standards (ERC20)
- The first standard was launched in November-2015 by Fabian Vogelsteller as an Ethereum Request for Comments (ERC). automatically assigned Github issue number 20, giving rise to the name “ERC20 token”.
- The of tokens are currently the ERC20 standard. ERC20 for fungible tokens, meaning that different units of an ERC20 token are interchangeable and unique properties.
- The ERC20 standard defines interface for contracts implementing a token, any compatible token accessed and way.
ERC20 Required functions and events
Returns units of this token that currently exist. ERC20 tokens can have or a variable supply.
Given an address, always returns the token balance of that address.
Given an address and amount, transfers of tokens address, from the balance of the address that executed the transfer.
Given a sender, recipient, and amount transfers tokens from one account . combination with approval.
Given a recipient address and amount, authorizes that address to execute several transfers up amount, from the account that issued the approval.
Given an owner address and a spender address, must return the remaining amount that the spender is approved to withdraw from the owner.
The event depends upon a successful transfer(call to transfer or transfer From) even for zero-value transfers.
Event logged upon a successful call to approve.