C / C++ / MFC

//Done in user application
int packageId = creatpackage(Function, arguments); // this create a package and adds it to a normal queue
wait(packageId); //wait call yeild function that is part of my library

//Inside library
void classname::yeild(int packageId){
   set the state of workpackage to Waiting
   add the package to WaitingQueue
if(there is another package in WaitingQueue)
      Make a switch context to it
else
     Go to normal queue and execute the package
}

#include<stdio.h>
#include<conio.h>
int main()
{
	double width,hight,area;
	printf("enter the value of width");
	scanf("%f",&width);
	printf("enter the vlaue of hight");
	scanf("%f",&hight);
	area=width*hight;
	printf("area=%f",area);
	return 0;
}
Why area=0.000 showing

WorkPackage PackageQueue::GetWorkPackage(){
	if (isEmpty())
	    {
		return WorkPackage(); // return an empty work package
	    }
		pthread_mutex_lock(&getlock);
		WorkPackage data=WorkPackageQueue[front];
	    if (front == rear)
	    {
	        rear = -1;
	        front = -1;
	    }

	    else if (front == 0)
	        front = size-1;
	    else
	        front--;
	     pthread_mutex_unlock(&getlock);
	     return WorkPackage(data);
	}

WorkPackage::WorkPackage(const WorkPackage& rhs){
	Wp_localstack.local_stack= Stack::make_stack();
	m_action=rhs.m_action;
	m_arguments=rhs.m_arguments;
}