Thread: Homework Struggles

I am writing a program that will act as a simple calculator when it is complete. The instructions state to use one function that returns 2 output parameters and another to do the calculations. I am stuck trying to get my accumulator to keep the result. This version runs but the last input is always the output that is printed. Any hints?

Code:

#include <stdio.h>
#include <math.h>


//Function prototypes
void scan_data (char *opp, double *nump);
void do_next_op (char op, double num, double *accup);

int main (void)

{
	//declare variables, not sure if the accumulator ACCU needs to be declared here
	double num, accu;
	char op;

	//Start do while loop to accept input from user until Q or q is chosen
	do
	{

	//Call functions until to get input and perform calculations
	scan_data(&op, &num);
	do_next_op (op, num, &accu);
	}
	while (op != 'q' && op != 'Q');

	//Print end result when Do While is exited
	printf ("The end result is %lf.\n", &accu);
}


//Get data function
void scan_data (char *opp, double *nump)

{
	double num;
	char op;
	printf ("Please enter an operator and number: ");
	scanf(" %c%lf", &op, &num);
	while (op != '+' && op != '-' && op != '*' && op != '/' && op != '^' && op != 'q' && op != 'Q')
		{
		fflush (stdin);
		printf ("Please enter an operator and Number: ");
		scanf(" %c %lf", &op, &num);
		}

		*opp = op;
		*nump = num;
}

//Here is where I think the problem lies, I reset the accumulator to 0 each time I enter the function, not sure how to fix it.
//I'm also not sure how to use the ACCU and *ACCUP as an input and output variable.
void do_next_op (char op, double num, double *accup)
{

	double accu = 0;

	if (op == '+')
	{
		*accup = accu + num;
		printf ("The result so far is %lf\n", *accup);
	}
	else if (op == '-')
	{
		*accup = accu - num;
	}

}