/*    File Name: assignone.cpp
*     Code Documented by      Bhavani Prasad Sangannagari

* This program is coded for the first assignment 
* that illustrates the concept of multi-threaded 
* programming

* This program shows how to create a new thread 
* using the _beginthread function. The actual work 
* in this program is done in the routine centofahr. This 
* routine takes a single argument (a void pointer) that 
* it casts to a float. The routine then calculates the 
* temperature in fahrenheit then prints the sum. 
 
* The main program converts celcius temperature into fahrenheit
* using the child thread and again computes the same without 
* using the child thread.
  
* The formula c/100 = (f-32)/180 is used for conversion by the
* function centofahr */ 


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

// function declaration 
void centofahr(void *);  


// global flag used to ensure main thread stops still child thread ends
char gflg = 'n';  

void main()
{
	//  cent accepts centigrade temperature from the user
	//  flg is used to verify if user wants to do more conversions
	float cent;
	char flg = 'y';


    cout<<"\n\tPROGRAM TO CONVERT TEMPERATURE FROM CENTIGRADE SCALE TO FAHRENHEIT SCALE";


	// this loop is used to repeat the program 
	// if the user wants to calculate more than one 
	// temperature conversions based on the value of flg
	// if entered y repeats else terminates program 
	
	while(flg == 'y') {
    
	// accept input in celcius
	cout<<"\n please enter the temperature in celcius :\t";
	cin>>cent;

	cout<<"\n This result is calculated using a thread";
	  
	  // beginthread function is used to start a new thread
	  // that calculates equivalent temperature in fahrenheit
	  // with default stack, cent as argument and using centofahr function
	
	_beginthread(centofahr,0,(void *) &cent);
    
	// this while loop is used to ensure the main thread waits
	// till the child thread completes execution
	while(gflg == 'n');
    

	cout<<"\n this result is obtained without using a thread";
	centofahr((void *) &cent);
	

	cout<<"\n would u like to do another convertion ? enter y or n   :";
	cin>>flg;
	
	gflg = 'n';

	}
}

/*     function : centofahr
			takes void pointer as argument
			does required calculation
			prints the result to the console */

void centofahr(void * celcius) {

	 float fahr, temp;
	temp = *(float *) celcius;

     fahr = (temp * 180)/100 + 32;
	 
     cout<<"\n"<<" In fahrenheit scale is "<<fahr<<"F\n"; 
	 fflush(stdout);
	 
	 gflg = 'y';
}