/***********************************************************************\
*	Name:		Program3												*
*	Purpose:	Allow user to perform basic mathematical operations		*		
*	Date:		04-12-06												*
*	Author:		Katharina van Santen									*
\***********************************************************************/

#include <stdio.h>										//include the stdio library

double add(double,double );								//declare a user defined library of add
double subtract(double,double );						//declare a user defined library of subtract
double multiply(double,double );						//declare a user defined library of multiply
double divide(double,double );							//declare a user defined library of divide

void main (void)										//declare the main function
{														//start the main function
	int choice;
	double x, y;
	double returned_sum;
	double returned_difference;
	double returned_product;
	double returned_quotient;
	
	printf("What would you like to do?\nPlease choose a number:\n");
	printf("1.\tAdd\n2.\tSubtract\n3.\tMultiply\n4.\tDivide\n5.\tEnd Program\n");
	scanf("%d", &choice);

	if (choice==1||choice==2||choice==3||choice==4)
	{
		printf("Please enter two numbers of type double\t");
		scanf("%lf%lf",&x,&y);
	}
	

		

	while (choice!=5)
	{
	if (choice==1)
	{
		add(x,y);
		returned_sum=add(x,y);
		printf("The sum of your two numbers %lf and %lf is %lf\n",x,y,returned_sum);
	}
	else if (choice==2)
	{
		subtract(x,y);
		returned_difference=subtract(x,y);
		printf("The difference of your two numbers %lf and %lf is %lf\n",x,y,returned_difference);
	}
	else if (choice==3)
	{
		multiply(x,y);
		returned_product=multiply(x,y);
		printf("The product of your two numbers %lf and %lf is %lf\n",x,y,returned_product);
	}
	else if (choice==4)
	{
		if (y!=0)
		{
		divide(x,y);
		returned_quotient=divide(x,y);
		printf("The quotient of your two numbers %lf and %lf is %lf\n",x,y,returned_quotient);
		}
		else
		printf("You cannot divide by 0!");
		
	}


	}

}


															//end the main function
double add(double x,double y)								
{															//start the add function
	double sum;
	sum=x+y;
	return sum;
}

															//end the add function
double subtract(double x,double y)
{															//start the subtract function
	double difference;
	difference=x-y;
	return difference;
}

															//end the subtract function
double multiply(double x,double y)
{															//start the multiply function
	double product;
	product=x*y;
	return product;
}

															//end the multiply function
double divide(double x,double y)
{															//start the divide function
	double quotient;
	quotient=x/y;
	return quotient;
}															//end the divde function