Ethereum, tokens & smart contracts.

Notes on getting started Part 7. ERC20 Token Standard

Previous notes in case you are just joining us:
Part 1. Setting up.
Part 2. Web3.js/node. 
Part 3. Solidity.
Part 4. Smart Contracts.
Part 5. Smarter Contracts.
Part 6. Tokens & Inheritance.

Better Tokens :

While you could use the minimal Token as the basis for your project, the good people at Ethereum have made available a more complex standard token which we will cover next, the erc20 token.

Note: Like everything in tech/blockchain development, things they are a changing, there is a new token standard proposal erc223 which might be implemented in the near future... and then something else will probably come along.

Sources:

• Github: https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20-token-standard.md
• Wiki: https://theethereum.wiki/w/index.php/ERC20_Token_Standard
• Ethereum.org: https://www.ethereum.org/token
• Medium: https://medium.com/@jgm.orinoco/understanding-erc-20-token-contracts-a809a7310aa5

In order to be part of the erc20 club, a token has to have the following functions and events (plus optional token information):

contract ERC20 {
 function totalSupply() constant returns (uint totalSupply);
 function balanceOf(address _owner) constant returns (uint balance);
 function transfer(address _to, uint _value) returns (bool success);
 function transferFrom(address _from, address _to, uint _value) returns (bool success);
 function approve(address _spender, uint _value) returns (bool success);
 function allowance(address _owner, address _spender) constant returns (uint remaining);
// events:
 event Transfer(address indexed _from, address indexed _to, uint _value);
 event Approval(address indexed _owner, address indexed _spender, uint _value);
// optional token information:
string public constant name = "Token Name";
string public constant symbol = "SYM";
 uint8 public constant decimals = 18;
}