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ballot.sol

pragma solidity ^0.4.0;
contract Ballot {

    struct Voter {
        uint weight;
        bool voted;
        uint8 vote;
        address delegate;
    }
    struct Proposal {
        uint voteCount;
    }

    address chairperson;
    mapping(address => Voter) voters;
    Proposal[] proposals;

    /// Create a new ballot with $(_numProposals) different proposals.
    function Ballot(uint8 _numProposals) public {
        chairperson = msg.sender;
        voters[chairperson].weight = 1;
        proposals.length = _numProposals;
    }

    /// Give $(toVoter) the right to vote on this ballot.
    /// May only be called by $(chairperson).
    function giveRightToVote(address toVoter) public {
        if (msg.sender != chairperson || voters[toVoter].voted) return;
        voters[toVoter].weight = 1;
    }

    /// Delegate your vote to the voter $(to).
    function delegate(address to) public {
        Voter storage sender = voters[msg.sender]; // assigns reference
        if (sender.voted) return;
        while (voters[to].delegate != address(0) && voters[to].delegate != msg.sender)
            to = voters[to].delegate;
        if (to == msg.sender) return;
        sender.voted = true;
        sender.delegate = to;
        Voter storage delegateTo = voters[to];
        if (delegateTo.voted)
            proposals[delegateTo.vote].voteCount += sender.weight;
        else
            delegateTo.weight += sender.weight;
    }

    /// Give a single vote to proposal $(toProposal).
    function vote(uint8 toProposal) public {
        Voter storage sender = voters[msg.sender];
        if (sender.voted || toProposal >= proposals.length) return;
        sender.voted = true;
        sender.vote = toProposal;
        proposals[toProposal].voteCount += sender.weight;
    }

    function winningProposal() public constant returns (uint8 _winningProposal) {
        uint256 winningVoteCount = 0;
        for (uint8 prop = 0; prop < proposals.length; prop++)
            if (proposals[prop].voteCount > winningVoteCount) {
                winningVoteCount = proposals[prop].voteCount;
                _winningProposal = prop;
            }
    }
}

ballot_test.sol

pragma solidity ^0.4.7;
import "remix_tests.sol"; // this import is automatically injected by Remix.
import "./ballot.sol";

contract test3 {
   
    Ballot ballotToTest;
    function beforeAll () {
       ballotToTest = new Ballot(2);
    }
    
    function checkWinningProposal () public {
        ballotToTest.vote(1);
        Assert.equal(ballotToTest.winningProposal(), uint(1), "1 should be the winning proposal");
    }
    
    function checkWinninProposalWithReturnValue () public constant returns (bool) {
        return ballotToTest.winningProposal() == 1;
    }
}

DataTypes.sol

pragma solidity ^0.4.0;

contract DataType {
    
    bool myBool = false;
    int8 myInt = -128;
    uint8 myUint = 255;
    
    string myString;
    uint8[] myStringArr;
    
    byte myValue;
    bytes1 myBytes1;
    bytes32 myBytes32;
    
    //fixed256x8 myFixed = 1; //255.0
    //ufixed myFixed = 1;
    
    enum Action {ADD, REMOVE, UPDATE}
    Action myAction = Action.ADD;
    
    address myAddress;
    
    function assignAddress() {
        myAddress = msg.sender; // It means that the person who actually deployed the contract
        myAddress.balance;
        myAddress.transfer(10);
    }
    
    // Defining Array with not fixed length
    
    uint[] myIntArr = [1, 2, 3];
    
    function arrFunc() {
        myIntArr.push(4);
        myIntArr.length;
        myIntArr[0];
    }
    
    // Defining Array of fixed length
    
    uint[10]myFixedArr;
    
    // Defining struct
    
    struct Account {
        uint balance;
        uint dailyLimit;
    }
    
    Account myAccount;
    
    function structFunc() {
        myAccount.balance = 100;
    }
    
    mapping (address => Account) _accounts;
    
    function() payable {
        _accounts[msg.sender].balance += msg.value;
    }
    
    function getBalance() returns (uint) {
        return _accounts[msg.sender].balance;
    }
    
    
    
    
}

Debugging.sol

pragma solidity ^0.4.0;

contract Debugging {
    uint[] private vars;
    
    // assignment is storing values in stack
    function assignment() {
        uint myVal1 = 1;
        uint myVal2 = 2;
        
        assert(myVal1 == myVal2);
    }
    
    function memoryAlloc() {
        string memory myString = "test";
        assert(bytes(myString).length == 10);
    }
    
    function storageAlloc() {
        vars.push(3);
        vars.push(4);
        
        assert(vars.length == 4);
    }
}

Strings.sol

pragma solidity ^0.4.0;

library Strings {
    
    function concat(string _base, string _value) internal returns (string) {
        // converting string to bytes
        
        bytes memory _baseBytes = bytes(_base); // Type casting values of string to bytes and defining the storage type of it.
        bytes memory _valueBytes = bytes(_value);
        
        string memory _tmpValue = new string(_baseBytes.length + _valueBytes.length); // Type casting bytes to string
        bytes memory _newValue = bytes(_tmpValue); // Now again type casting string to bytes
        
        uint i; // its iterator over given value. i.e, _baseBytes, _valueBytes
        uint j; // its iterator over new value
        
        for(i=0; i< _baseBytes.length; i++) {
            _newValue[j++] = _baseBytes[i];
        }
        
        for(i=0; i< _valueBytes.length; i++) {
            _newValue[j++] = _valueBytes[i];
        }
        
        return string(_newValue);
    }
    
    function strPos(string _base, string _value) internal returns(int) {
         bytes memory _baseBytes = bytes(_base); 
         bytes memory _valueBytes = bytes(_value);
         
         assert(_valueBytes.length == 1);
         
         for(uint i = 0; i< _baseBytes.length; i++) {
            if(_baseBytes[i] == _valueBytes[0]) {
                return int(i);
            } 
         }
         
         return -1;
    }
    
    function substring(string str, uint startIndex, uint endIndex) constant returns (string) {
        bytes memory strBytes = bytes(str);
        bytes memory result = new bytes(endIndex-startIndex);
        for(uint i = startIndex; i < endIndex; i++) {
            result[i-startIndex] = strBytes[i];
        }
        return string(result);
    }
}

contract TestStrings {
    
        using Strings for string;
        
        function testConcat(string _base) returns (string) {
            return _base.concat("_suffix");
        }
        
        function needleInHayStack(string _base) returns (int) {
            return _base.strPos("t");
        } 
        
        function findSubStringFromString(string _base) returns (string) {
            return _base.substring(4, 25);
        }
}

pragma solidity ^0.4.0;

contract DataType {

bool myBool = false;
int8 myInt = -128;
uint8 myUint = 255;

string myString;
uint8[] myStringArr;

byte myValue;
bytes1 myBytes1;
bytes32 myBytes32;

//fixed256x8 myFixed = 1; //255.0
//ufixed myFixed = 1;

enum Action {ADD, REMOVE, UPDATE}
Action myAction = Action.ADD;

address myAddress;

function assignAddress() {
    myAddress = msg.sender; // It means that the person who actually deployed the contract
    myAddress.balance;
    myAddress.transfer(10);
}

// Defining Array with not fixed length

uint[] myIntArr = [1, 2, 3];

function arrFunc() {
    myIntArr.push(4);
    myIntArr.length;
    myIntArr[0];
}

// Defining Array of fixed length

uint[10]myFixedArr;

// Defining struct

struct Account {
    uint balance;
    uint dailyLimit;
}

Account myAccount;

function structFunc() {
    myAccount.balance = 100;
}


// mapping (_KeyType => _ValueType) mapName.
// Here we can look for the Ethereum address of Account and then fetch the values of those Account. i.e, balance, dailyLimit
mapping (address => Account) _accounts;


// payable is a keyword which means that you can collect/receive funds in your contract.
// All the ethers sent to payable functions are owned by contract. 
// Payable fallback functions : A function without any name and annotated with payable keyword is called payable fallback function. There could be only one such function in contract.


function() payable {
    _accounts[msg.sender].balance += msg.value;
}

function getBalance() returns (uint) {
    return _accounts[msg.sender].balance;
}

}