Question based on exit(1)

[thecodeinnovator]

Why is the user not able to view output messages before exit(1); how to rectify this ?

#include<iostream.h>
#include<process.h>

int sum(int &x,int &y)
{
	return (x+y);
}

int main()
{
	int a,b;
	do
	{
		cout<<"\nEnter 2 Values : ";
		cin>>a>>b;
		cout<<"\nThe Sum is : "<<sum(a,b);
		cout<<"\nDo You Want to continue ?(y/n)..."
		cin>>ch;
	}while((ch=='y')||(ch=='Y'));
	if((ch!='y')||(ch!='Y'))
	{
		cout<<"\nThankyou for using the Program !!!";	//This output is not clearly given to the user when he exits the program (WHY...?)?
		exit(1);										//How can we rectify this problem ?
	}
	return 0;
}

[AbstractionAnon]

http://www.cplusplus.com/forum/beginner/1988/

[thecodeinnovator]

thank you @AbstractionAnon

but can this be added ??

for(int i=0;i<500;i++)
{
              //Null for loop to create pause ( becoz im using c++2003)(school oriented !!)
}

[MiiNiPaa]

Null for loop to create pause

This will not work. Any compiler worth using will simply throw that loop away as it does nothing and there is no sense in even executing it.

Not to mention that if it would include loop, you are making busi wait, eating PC resources.

And most important: There is no guarantee that text will actually be outputted before that loop.

[thecodeinnovator]

But i am adding it 'HERE' :

if((ch!='y')||(ch!='Y'))
{
	cout<<"\nThankyou for using the Program !!!";
                                          //Here	
	exit(1);										
}

Like this :

#include<iostream.h>
#include<process.h>

int sum(int &x,int &y)
{
	return (x+y);
}

int main()
{
	int a,b;
	do
	{
		cout<<"\nEnter 2 Values : ";
		cin>>a>>b;
		cout<<"\nThe Sum is : "<<sum(a,b);
		cout<<"\nDo You Want to continue ?(y/n)..."
		cin>>ch;
	}while((ch=='y')||(ch=='Y'));
	if((ch!='y')||(ch!='Y'))
	{
		cout<<"\nThankyou for using the Program !!!";
                for(int i=0;i<500;i++)
                {
                                       //Like this   ----->NULL LOOP
                }
		exit(1);										
	}
	return 0;
}

what about now ???

[MiiNiPaa]

Nothing. (1) compiler is likel to optimize away that loop
(2) consider this:

cout<<"\nThankyou for using the Program !!!"; //Nothing displayed yet, buffer is not flushed
//<useless loop>
exit(1); //Now, after exit call, during destruction of static objects, cout buffer is flushed and text is actually displayed. 

You can actually manually flush input buffer but it is not a good idea. It just masks the problem instead of solving it _{^{(not to mention that busy waiting is worst thing you can do)}}. Correct way is to configure your IDE properly. (for visual studio run with ctrl+F5). If you are running outside IDE, run as it is intended: through comand line.

[JLBorges]

To force a stream to write out buffered output immediately, flush it.

#include <iostream>
#include <cstdlib>
#include <thread>
#include <chrono>

int main()
{
    // flush: http://en.cppreference.com/w/cpp/io/manip/flush
    // flush std::cout before the spawned process writes to stdout
    std::cout << "you are: " << std::flush ;
    std::system( "whoami" ) ;

    // flush std::cout before entering a wait state
    std::cout << "thank you for using the program!\n" << std::flush ;
    std::this_thread::sleep_for( std::chrono::seconds(2) ) ;
}