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  • Jun 05 2016 10:31
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Pawan Singhal

this is the code: pragma solidity ^0.4.2;
contract tokenRecipient { function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData); }

contract MyToken {
/ 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 MyToken(
    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 approve(address _spender, uint256 _value)
    returns (bool success) {
    allowance[msg.sender][_spender] = _value;
    return true;

/* Approve and then comunicate the approved contract in a single tx */
function approveAndCall(address _spender, uint256 _value, bytes _extraData)
    returns (bool success) {
    tokenRecipient spender = tokenRecipient(_spender);
    if (approve(_spender, _value)) {
        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


Pawan Singhal
How can I retrieve the password of my Ethereum wallet, I have forgotten it?
Vlad Suciu
Are there any tutorials about state channels? Can there be state channels with more than 2 participants? how are they implemented?
Hi all! is it possible to set rules
regarding coin/token issuance: is it possible to set rules based on external data? through API for example
2) when issuing new coins/token is it possible to distribute proportionally to actual token's owner?
Vlad Suciu
thank you
Is Reputation Fungible?
Can we have a bit of democracy, reputation, awards, and safeties built into our smart contracts. And what are the man hours required?
Artem Gorev
Hello, guys. Have anyone know what need to read to understand how wallets, accounts are created inside ethereum network? :-)
can you create a currency to be specifically used by people from one country
or peg it to another currency
such as a cryptocurrency pegged to the mozambique kwacha
or the zimbabwe dollar
for use in those countries - with the only aim of digitising the national currency on an unofficial basis
I would like to ask how to use the Ethereal Block Chain to store and transmit data as objects having structure apart from currency?
Vlad Suciu
hello, are there any tutorials for new Ethereum developers about Ethereum clients?
best practices/tips/etc
can I ask here some questions about solidity?
there seems to be an issue with developing using the eth wallet, i cant seem to generate a construction parameters as per the guide. any advice?
hi im new to ethereum whats the best newbie start up guide or video
Eric Stermer
from what I am learning, there are a couple things to understand
and someone can correct me if i am wrong
Ethereum is like a database on the backend that resides on a blockchain which exists in the world computer
it basically is written in solidity which is a newly created "Contract Oriented Language" which triggers exchange events in that blockchain
and just like any backend there is a front end that goes with it, which in the case of ethereum, the front end client is called Mist
which is like your chrome browser for ethereum
where in mist you can use standard HTML, CSS, and JS and all other frameworks and libraries to design websites to interact with contracts
So it is up to you whether you want to learn how to write general website programming or contract writing in Solidity
Eric Stermer
There is a new Solidity environment to learn in that is right in the browser and you can find that here:
Also check out Metamask as a Mist substitute. Tutorial: https://gist.github.com/flyswatter/aea93752fb90322bbe11
I created a contract on https://ethereum.github.io and am logged in my Metamask test account but metamask is not popping up in my browser in order to accept the transaction and create the contract?
Abhijit Roy
what are the pre-requisite for a developer who want to build app on Ethereum?
Rocky Fikki
Network and their security, solidity and general dapp best practices expertise, javascript or such other frontend stack capabilities.
Abhijit Roy
programming languages needed??
Rocky Fikki
solidity, and whatever frontend scripting/language knowledge is required. it might help if you have familiarity of the code the ethereum client is written in, but that is not a necessity.
Neo Wenyuan
hey guys, i'm just wondering
for the tokens that i've created using ethereum wallet, can it be listed on coinmarketcap? lols
hi, im working in the french bank BNP PARIBAS, i have business project
and i can listen all projecc very interesed
Geoff McNeely
I'm following the token tutorial and got confused as it moved to Centralized Administrator. Can someone give me some guidance? When it talks about inheritance and directs me to add a line of code, well, the contract was previously deployed and I can't seem to edit it, so what am I supposed to do? Create a new contract?
(this is my first tutorial for learning ethereum dApps so very green)
Neo Wenyuan
\@geoster hi there, i'm now as well, but been past your phase
@geoster basically, just do not deploy the contract yet until you finished reading the whole page, and do the customization you may need.
@ccvman what are u interested in?