Format readme.md

Readme.md

@@ -1,12 +1,26 @@
-Part of the course on "Ethereum Blockchain DAPP Development"
+## Part of the course on "Ethereum Blockchain DApp Development"
 http://www.ACloudFan.com
 
-MAC/UBUNTU/LINUX Users:
+### MAC/UBUNTU/LINUX Users:
+Please rename truffle-config.js to config.js
 
-Please rename truffle-config to config.js
+### Sample Contracts
+The following sample smart contracts are used across several lectures:
+* Calculator
+* CalculatorV2
+* CalculatorV3
+* interactionChannel
 
-Calculator/CalculatorV2/interactionChannel contract is used as a sample in lectures in the course
+### Objectives
+The aim is to achieve the following objectives:
+1. Introduction to DApp development
+2. Demonstrate the use of various wallets
+3. How to manage smart contracts
+4. Introduction to Remix
+5. Demonstrate the use of a browser based Solidity IDE for smart contract development
+6. Development of contracts using Truffle framework
 
-1  DAPP development sample and for demonstrating the use of wallets for managing contracts
-2. For demonstrating use of Broweser based Solidity contract development
-2. Development of contracts using Truffle framework
+#### Legend:
+- DApp: Decentralised Application
+- IDE: Integrated Development Environment
+- Remix: Solidity IDE

contracts/CalculatorV3.sol

@@ -0,0 +1,58 @@
+// pk: changed to latest version 0.4.23
+pragma solidity ^0.4.23;
+
+// pk: changed the contract version from 2 to 3
+contract CalculatorV3 {
+
+    uint result;
+
+    event NumberAdded(uint n);
+    event NumberSubtracted(uint n);
+    event NumberMultiplied(uint n);
+    event NumberDivided(uint n);
+
+    // pk: changed the function name to something other than the contract name
+    function Calculator(uint num) public {
+        // constructor
+        result = num;
+    }
+
+    // returns the result
+    // pk: "constant" deprecated, replaced with "view"
+    function getResult() public view returns (uint){
+        return result;
+    }
+
+    // result = result + num
+    function addToNumber(uint num) public returns (uint) {
+        result += num;
+        // pk: inserted "emit" before  calling the event
+        emit NumberAdded(num);
+        return result;
+    }
+
+    // result = result - num
+    function substractNumber(uint num) public returns (uint) {
+        result -= num;
+        // pk: inserted "emit" before  calling the event
+        emit NumberSubtracted(num);
+        return result;
+    }
+
+    // result = result * num
+    function multiplyWithNumber(uint num) public returns (uint) {
+        result *= num;
+        // pk: inserted "emit" before  calling the event
+        emit NumberMultiplied(num);
+        return result;
+    }
+
+    // result = result / num
+    function divideByNumber(uint num) public returns (uint) {
+        result /= num;
+        // pk: inserted "emit" before  calling the event
+        emit NumberDivided(num);
+        return result;
+    }
+
+}