I hope someone can help me. I think I'm on the right track but am missing a piece of the puzzle. I'm hoping, wishing (okay begging) someone to take a look at my program and provide me with some feedback. Please let me know if I'm completely off base or what.
The program is an invoice. The user inputs the invoice cost, then inputs the discount code. Based on the code used the discount rate is determined. Using a function I am to calculate the discount amount. The program should return the initial invoice cost, discount amount and final invoice cost.
Thanks,
Angela


Code:
#include<stdio.h>

/* Program will calculate customer's discount based on code entered by user*/
/* At program's termination the initial invoice amount, discount amount and
   final invoice cost will be display.*/
   
float Calc_Discount();
void Display_Results();

int main()
{
	extern float initial_invoice_amount, discount_amount, final_cost;
	extern char discount_code;
	
	/*Display dicount percent with mathching code*/
	printf("Discount code A = 5%%.\n");
	printf("Discount code B = 8%%.\n");
	printf("Discount code C = 12%%.\n");
	
	/*User Input*/
	printf("Input the customer's invoice amount:\n");
	scanf("%f", & initial_invoice_amount);
	
	printf("Input the customer's discount code:\n");
	scanf("%c", &discount_code);
		
		
	final_cost = (initial_invoice_amount - discount_amount);
		
	Display_Results();
	
	return 0;
	}	 
		  Calc_Discount(discount_code)
		   {
		     if((discount_code='A') || (discount_code='a'))
		      {
		        discount_amount == (0.05*initial_invoice_amount);
		      }
		     return discount_amount;
		     
		    if((discount_code='B') || (discount_code='b'))
		     {
		       discount_amount == (0.08*initial_invoice_amount);
		     }
		    return discount_amount;
		    
		    if((discount_code='C') || (discount_code='c'))
		     {
		       discount_amount == (0.12*initial_invoice_amount);
		     }
		      return discount_amount;
		   }
		      
		  void Display_Results(float initial_invoice_amount,float discount_amount, float final_cost)
		  {
		    printf("\nThe invoice charges are as follows:\n");
		    printf("\nInitial Invoice: %f", initial_invoice_amount);
		    printf("\nDiscount Amount: %f", discount_amount);
		    printf("\n--------------------------");
		    printf("\nFinal Cost: %f", final_cost);
		 }
		   
		      
	
}