A token with transfers and allowance spending, and an owner who can mint new units, deployed June 2016.
Historical Significance
The advanced token from the ethereum.org tutorial puts a market inside the token: the owner sets a buy and a sell price and holders trade against the contract's own ether balance rather than finding a counterparty. It is an automated market maker with a fixed price and no curve, written years before the term existed, and it fails the same way each time, since the contract will keep quoting a price it can no longer honour once its balance runs out. The owner also mints and freezes, so every risk in the design is concentrated in one account.
Context
Homestead arrived in March 2016 and the ethereum.org tutorials were rewritten around the transfer and balanceOf names that ERC-20 was standardising. Deploying a token had become a matter of filling in four constructor arguments, and most of the deployments of this period are exactly that.
Token Information
Key Facts
Description
A token from the ethereum.org tutorial. Balances sit in a public balanceOf mapping and transfer(to, value) moves them, throwing rather than returning false when the sender is short and checking the recipient's balance for overflow before adding to it. An allowance mapping records what each spender has been authorised for. ApproveAndCall sets the allowance and calls receiveApproval on the spender in the same transaction, so a spending contract learns of its allowance at the moment it is granted. The owner can create new units, freeze an account so it can no longer send, set a buy and a sell price at which holders trade against the contract's own ether balance and hand the role to another address. It was deployed as Schrute Buck, with the symbol SB and an opening supply of 0 base units at 2 decimal places and it answers standard() with the string Token 0.1, the label the tutorial used before ERC-20 had a number.
Source Verified
Historian Categories
Heuristic Analysis
The following characteristics were detected through bytecode analysis and may not be accurate.
Homestead Era
The first planned hard fork. Removed the canary contract, adjusted gas costs.
Bytecode Overview
Verified Source Available
Source verified through compiler archaeology and exact bytecode matching.
View Verification ProofShow source code (Solidity)
// Submitted by EthereumHistory (ethereumhistory.com)
contract owned {
address public owner;
function owned() {
owner = msg.sender;
}
modifier onlyOwner {
if (msg.sender != owner) throw;
_
}
function transferOwnership(address newOwner) onlyOwner {
owner = newOwner;
}
}
contract tokenRecipient { function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData); }
contract token {
/* Public variables of the token */
string public standard = 'Token 0.1';
string public name;
string public symbol;
uint8 public decimals;
uint256 public totalSupply;
/* This creates an array with all balances */
mapping (address => uint256) public balanceOf;
mapping (address => mapping (address => uint256)) public allowance;
/* This generates a public event on the blockchain that will notify clients */
event Transfer(address indexed from, address indexed to, uint256 value);
/* Initializes contract with initial supply tokens to the creator of the contract */
function token(
uint256 initialSupply,
string tokenName,
uint8 decimalUnits,
string tokenSymbol
) {
balanceOf[msg.sender] = initialSupply; // Give the creator all initial tokens
totalSupply = initialSupply; // Update total supply
name = tokenName; // Set the name for display purposes
symbol = tokenSymbol; // Set the symbol for display purposes
decimals = decimalUnits; // Amount of decimals for display purposes
}
/* Send coins */
function transfer(address _to, uint256 _value) {
if (balanceOf[msg.sender] < _value) throw; // Check if the sender has enough
if (balanceOf[_to] + _value < balanceOf[_to]) throw; // Check for overflows
balanceOf[msg.sender] -= _value; // Subtract from the sender
balanceOf[_to] += _value; // Add the same to the recipient
Transfer(msg.sender, _to, _value); // Notify anyone listening that this transfer took place
}
/* Allow another contract to spend some tokens in your behalf */
function approveAndCall(address _spender, uint256 _value, bytes _extraData)
returns (bool success) {
allowance[msg.sender][_spender] = _value;
tokenRecipient spender = tokenRecipient(_spender);
spender.receiveApproval(msg.sender, _value, this, _extraData);
return true;
}
/* A contract attempts to get the coins */
function transferFrom(address _from, address _to, uint256 _value) returns (bool success) {
if (balanceOf[_from] < _value) throw; // Check if the sender has enough
if (balanceOf[_to] + _value < balanceOf[_to]) throw; // Check for overflows
if (_value > allowance[_from][msg.sender]) throw; // Check allowance
balanceOf[_from] -= _value; // Subtract from the sender
balanceOf[_to] += _value; // Add the same to the recipient
allowance[_from][msg.sender] -= _value;
Transfer(_from, _to, _value);
return true;
}
/* This unnamed function is called whenever someone tries to send ether to it */
function () {
throw; // Prevents accidental sending of ether
}
}
contract MyAdvancedToken is owned, token {
uint256 public sellPrice;
uint256 public buyPrice;
uint256 public totalSupply;
mapping (address => bool) public frozenAccount;
/* This generates a public event on the blockchain that will notify clients */
event FrozenFunds(address target, bool frozen);
/* Initializes contract with initial supply tokens to the creator of the contract */
function MyAdvancedToken(
uint256 initialSupply,
string tokenName,
uint8 decimalUnits,
string tokenSymbol,
address centralMinter
) token (initialSupply, tokenName, decimalUnits, tokenSymbol) {
if(centralMinter != 0 ) owner = centralMinter; // Sets the owner as specified (if centralMinter is not specified the owner is msg.sender)
balanceOf[owner] = initialSupply; // Give the owner all initial tokens
}
/* Send coins */
function transfer(address _to, uint256 _value) {
if (balanceOf[msg.sender] < _value) throw; // Check if the sender has enough
if (balanceOf[_to] + _value < balanceOf[_to]) throw; // Check for overflows
if (frozenAccount[msg.sender]) throw; // Check if frozen
balanceOf[msg.sender] -= _value; // Subtract from the sender
balanceOf[_to] += _value; // Add the same to the recipient
Transfer(msg.sender, _to, _value); // Notify anyone listening that this transfer took place
}
/* A contract attempts to get the coins */
function transferFrom(address _from, address _to, uint256 _value) returns (bool success) {
if (frozenAccount[_from]) throw; // Check if frozen
if (balanceOf[_from] < _value) throw; // Check if the sender has enough
if (balanceOf[_to] + _value < balanceOf[_to]) throw; // Check for overflows
if (_value > allowance[_from][msg.sender]) throw; // Check allowance
balanceOf[_from] -= _value; // Subtract from the sender
balanceOf[_to] += _value; // Add the same to the recipient
allowance[_from][msg.sender] -= _value;
Transfer(_from, _to, _value);
return true;
}
function mintToken(address target, uint256 mintedAmount) onlyOwner {
balanceOf[target] += mintedAmount;
totalSupply += mintedAmount;
Transfer(0, owner, mintedAmount);
Transfer(owner, target, mintedAmount);
}
function freezeAccount(address target, bool freeze) onlyOwner {
frozenAccount[target] = freeze;
FrozenFunds(target, freeze);
}
function setPrices(uint256 newSellPrice, uint256 newBuyPrice) onlyOwner {
sellPrice = newSellPrice;
buyPrice = newBuyPrice;
}
function buy() {
uint amount = msg.value / buyPrice; // calculates the amount
if (balanceOf[this] < amount) throw; // checks if it has enough to sell
balanceOf[msg.sender] += amount; // adds the amount to buyer's balance
balanceOf[this] -= amount; // subtracts amount from seller's balance
Transfer(this, msg.sender, amount); // execute an event reflecting the change
}
function sell(uint256 amount) {
if (balanceOf[msg.sender] < amount ) throw; // checks if the sender has enough to sell
balanceOf[this] += amount; // adds the amount to owner's balance
balanceOf[msg.sender] -= amount; // subtracts the amount from seller's balance
msg.sender.send(amount * sellPrice); // sends ether to the seller
Transfer(msg.sender, this, amount); // executes an event reflecting on the change
}
}External Links
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