basic_ostream::flush

Forces the output buffer to release its contents.

  basic_ostream<charT, traits>& flush();
  

The function flush() is an output only function in C++. You may use it for an immediate expulsion of the output buffer. This is useful when you have critical data or you need to ensure that a sequence of events occurs in a particular order. If the operation fails, it calls setstate(badbit).

The this pointer is returned.

Note that in the Example of basic_ostream::flush() usage: if you comment out the flush both lines will display simultaneously at the end of the program.

#include <iostream>
#include <iomanip>

#include <ctime>

class stopwatch {

private:

   double begin, set, end;    

public:

   stopwatch();

   ~stopwatch();

   void start();

   void stop();

};

stopwatch::stopwatch() 

{      

using namespace std;

                

   begin = (double) clock() / CLOCKS_PER_SEC; 

   end    = 0.0; 

   start();

   cout << "begin the timer: ";

}

stopwatch::~stopwatch() 

{

using namespace std;

   stop();    // set end

   cout << "\nThe Object lasted: ";

   cout << fixed << setprecision(2)

      << end - begin << " seconds \n";

}

// clock ticks divided by ticks per second

void stopwatch::start() 

{

using namespace std;

   set = double(clock()/CLOCKS_PER_SEC);

}

void stopwatch::stop() 

{

using namespace std;

   end = double(clock()/CLOCKS_PER_SEC);

}

void time_delay(unsigned short t);

int main()

{

using namespace std;

   stopwatch watch; // create object and initialize 

   cout.flush(); // this flushes the buffer 

   time_delay(5);      

   return 0; // destructor called at return

}

      //time delay function

void time_delay(unsigned short t)

{

using namespace std;

   time_t tStart, tEnd;

   time(&tStart);

   while(tStart + t > time(&tEnd)){};

}

Result:

  begin the timer: < immediate display then pause >
  begin the timer: 
  The Object lasted: 3.83 seconds