MyToken

// Submitted by EthereumHistory (ethereumhistory.com)
contract tokenRecipient { function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData); }

contract MyToken { 
    /* Public variables of the token */
    string public name;
    string public symbol;
    string public version;
    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;
    mapping (address => mapping (address => uint256)) public spentAllowance;

    /* 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 MyToken(uint256 initialSupply, string tokenName, uint8 decimalUnits, string tokenSymbol, string versionOfTheCode) {
        balanceOf[msg.sender] = 21000000;              // 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        
        version = versionOfTheCode;
    }

    /* 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 (spentAllowance[_from][msg.sender] + _value > allowance[_from][msg.sender]) throw;   // Check allowance
        balanceOf[_from] -= _value;                          // Subtract from the sender
        balanceOf[_to] += _value;                            // Add the same to the recipient            
        spentAllowance[_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
    }        
}