### A simple approach to generate Fibonacci series via multi-threading

This is a very simple approach taken to generate the Fibonacci series through multithreading. Here instead of a function, used a function object. The code is very simple and self-explanatory.

#include <iostream>
#include <mutex>

class Fib {
public:
Fib() : _num0(1), _num1(1) {}
unsigned long operator()();

private:
unsigned long _num0, _num1;
std::mutex mu;
};

unsigned long Fib::operator()() {
mu.lock(); // critical section, exclusive access to the below code by locking the mutex
unsigned long  temp = _num0;
_num0 = _num1;
_num1 = temp + _num0;
mu.unlock();
return temp;
}

int main()
{
Fib f;

int i = 0;
unsigned long res = 0, res2= 0, res3 = 0;
std::cout << "Fibonacci series: ";

while (i <= 15) {
std::thread t1([&] { res = f(); }); // Capturing result to respective variable via lambda
std::thread t2([&] { res2 = f(); });
std::thread t3([&] { res3 = f(); });

t1.join();
t2.join();
t3.join();

// Arranging in order, since threads execution can be random,
// So the result may not be in order to display

if (res > res3) std::swap(res, res3);
if (res > res2) std::swap(res, res2);
if (res2 > res3) std::swap(res2, res3);

std::cout << res << " " << res2 << " " << res3 << " ";
i += 3;
}
}

We can use std::lock_guard like below to give RAII style mechanism for owning the mutex during the scoped block.

unsigned long Fib::operator()()
{
// critical section, exclusive access to the below code by locking a mutex by lock_guard
std::lock_guard<std::mutex> lock(mu);
unsigned long  temp = _num0;
_num0 = _num1;
_num1 = temp + _num0;
return temp;
}

### Reversing char array without splitting the array to tokens

I was reading about strdup, a C++ function and suddenly an idea came to my mind if this can be leveraged to aid in reversing a character array without splitting the array into words and reconstructing it again by placing spaces and removing trailing spaces. Again, I wanted an array to be passed as a function argument and an array size to be passed implicitly with the array to the function. Assumed, a well-formed char array has been passed into the function. No malformed array checking is done inside the function. So, the function signature and definition are like below: Below is the call from the client code to reverse the array without splitting tokens and reconstructing it. Finally, copy the reversed array to the destination.  For GNU C++, we should use strdup instead _strdup . On run, we get the following output: Demo code

### Close a Window Application from another application.

This is just a demo application code to show how the WM_CLOSE message can be sent to the target process which has a titled window to close the application. To achieve this, either we can use SendMessage or PostMessage APIs to send required Windows messages to the target application. Though both the APIs are dispatching WM_XXXXX message to target application two APIs has some differences, these are as below: 1. SendMessage () call is a blocking call but PostMessage is a non-blocking call(Asynchronous) 2. SendMessage() APIs return type is LRESULT (LONG_PTR) but PostMessage() APIs return type is BOOL(typedef int). In Short, SendMessage () APIs return type depends on what message has been sent to the Windowed target process. For the other one, it's always a non-zero value, which indicates the message has been successfully placed on the target process message queue. Now let's see how can I close a target windowed application "Solitaire & Casual Games" from my custom-

### XOR (Exclusive OR) for branchless coding

The following example shows the array reversing using the  XOR operator . No need to take any additional variable to reverse the array.   int main(int argc, _TCHAR* argv[]) { char str[] = "I AM STUDENT"; int length = strlen(str); for(int i = 0; i < ((length/2)); i++) { str[i] ^= str[length - (1+i)]; str[length - (1+i)] ^= str[i]; str[i] ^= str[length - (1+i)]; } cout << str << endl; return 0; } The above example is one of the uses of XOR but XOR comes in handy when we can do branchless coding  methods like butterfly switch etc. Sometimes this is very effective in speeding up the execution.  Let's see one of the uses of XOR in branchless coding. I am taking a simple example of Y = | X |.  Yes, I am generating abs of a supplied number. So, my function signature/definition in C++ looks like below: int absoluteBranch( int x) {     if (x < 0 ) {         return -x;     }     else {         retur