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Respect I think it's time to talk about currency. Let's create a Respect Coin. Step 1. Install OpenZeppelin library  npm install zeppelin-solidity When it comes to coins, I like to use some functions that smart people already implemented and other smart people verified. I think that Zeppelin is a nice collection of Solidity contracts that can be trusted. Let's use the StandardToken contract and use it as a parent class for our own RespectCoin contract. Step 2. Create RespectCoin contract and store it in "contracts/RespectCoin.sol" file  pragma solidity ^0.4.4; import "../node_modules/zeppelin-solidity/contracts/token/StandardToken.sol"; /** * @title RespectCoin * @dev ERC20 Token example, where all tokens are pre-assigned to th e creator. * Note they can later distribute these tokens as they wish using `transfer` and other * `StandardToken` functions. */ contract RespectCoin is StandardToken { string public constant name = ...

Friend of mine pointed out that the "Hello World" contract described in my previous post does not keep state. Reading and writing data to the blockchain is important and can be challenging. In this post I will add a counter to count number of times the sayHello() function was called.    Step 1. Create  a new contract Let's create a file HelloWithCounter.sol and put it into the "contracts" directory. pragma solidity ^0.4.4; contract HelloWithCounter { uint private helloCounter; function Hello() public { // constructor helloCounter = 0; } function sayHello() public returns (string) { helloCounter = helloCounter+1; return strConcat('I say Hello #', uintToString(helloCounter)); } function getHelloCounter() constant public returns (string) { return uintToString(helloCounter); } function uintToString(uint v) internal pure returns (string str) { uint maxlength = 100; bytes memory reversed = new byt...

How to say "Hello World" in the era of blockchain? Reflections Once upon a time, I worked in CTO role of a great startup, and in order to find talented code developers, we ran a competition for the most creative "Hello World" application. It was a lot of fun! I was not able to participate in the competition back then, but here is my delayed entry. Step 1. Environment Configuration # Installing Truffle framework (http://truffleframework.com/) $ sudo npm install -g truffle # Creating project $ mkdir solidity-experiments $ cd solidity-experiments/ $ truffle init # Installing and starting Etherium local test network $ sudo npm install -g ethereumjs-testrpc $ testrpc & Step 2. Point truffle framework to the test network Update truffle.js file created by the init to point to your test network. File content should look like this: module.exports = { networks: { development: { host: "localhost", port: 8545, network_id: "*" ...