Ohh so close to getting the program to do what is required!!
Below is the code. I have two problems I have not been able to figure out:
1) I need input to accept only integer input (but as is it will accept float type)
2) On the "division" printf statement, I can get it to echo the inputted values and the x/y correctly, but cannot get the remainder to display correctly. Can anyone help with the simple solutions that I cannot seem to figure out?
Thanks!!!

Code:
#include <stdio.h>
int remainder ;
int addint (int x, int y); /*Function Prototypes for actions*/
int subint (int x, int y); /* to be performed on input */
int multint (int x, int y);
int divideint (int x, int y, int z);
int powerint (int x, int y);
int gcdint (int x, int y);
int factorial (int x);

int main()
{

   int x=0;  /* Variable initializations */
   int y=0;
   int z=0;
   char select;
   printf("This program will perform one of the following operations \n"); /* User Menu for program */
   printf("to two numbers based on your selection from the following menu: \n \n");
   printf("1. Add two integers. \n");
   printf("2. Subtract two integers. \n");
   printf("3. Multiply two integers. \n");
   printf("4. Divide two integers. \n");
   printf("5. Calculate integer raised to a positive power. \n");
   printf("6. Compute greatest common divisor of two integers. \n");
   printf("7. Compute the factorial of an integer. \n \n");
   printf("To quit the program at any time, please press q or Q. \n \n");
   printf("Please enter two integers: \n\n"); /* Prompt user for two integers */
   fflush(stdin);
   scanf("%d", &x);
   scanf("%d", &y);
   printf("Please choose desired operation from above menu. \n "); /* Prompt user to select desired action */
   fflush(stdin);
   scanf("%c", &select);
    while (select != 'q' && select != 'Q') /* Continues running program unitl sentinel value entered */
	{
  
	   switch (select)  /* Invoke the proper function to perform required action */
	   {
    	case '1':
	    printf("\n The sum of  %d and  %d is  %d.", x, y,addint(x,y));
	    break;

        case '2':
	    printf("\n %d minus  %d is  %d", x, y, subint(x,y));
	    break;

	    case '3':
	    printf("\n %d multiplied by  %d is  %d", x, y, multint(x,y));
	    break;

	    case '4':
		if(y >0)
		 printf("\n %d divided by %d is   %d and remainder is %d", x,y,divideint(x,y,z));
		else /*Else statement to handle division by 0 */
		 printf("\n Error,  division by 0.  \n"); 
		break;

	    case '5':
		 if (y>=0)
	      printf("\n %d raised to power of %d is  %d ", x, y, powerint(x,y));
		 else /*Else statement to handle raising to a negative power */
	      printf("\n You cannot raise a number to a negative power!\n");	  
	    break;

	    case '6':
	    printf("\n The greatest common denominator of %d and %d is %d", x, y, gcdint(x,y));
	    break;

	    case '7':
	     if (x<0 || y<0) /*if statement to handle a negative factorial */

	      printf("\n Error, negative factorial value entered. \n");
	     else
	      printf("\n The value of the factorial for %d is    %d \n", x, factorial(x));
	      printf("\n The value of the factorial for %d is    %d", y, factorial(y));
	  
        break;

        default: 
         printf("Incorrect value entered, please reenter. \n \n");
        break;
	
  }
 
   printf("\n \n This program will perform one of the following operations \n"); /* Reposts "menu" and reprompts user for input */
   printf("to two numbers based on your selection from the following menu: \n \n");
   printf("1. Add two integers. \n");
   printf("2. Subtract two integers. \n");
   printf("3. Multiply two integers. \n");
   printf("4. Divide two integers. \n");
   printf("5. Calculate integer raised to a positive power. \n");
   printf("6. Compute greatest common divisor of two integers. \n");
   printf("7. Compute the factorial of an integer. \n \n");
   printf("To quit the program, please press q or Q. \n \n");
   printf("Please enter two integers: \n\n");
   fflush(stdin);
   scanf("%d", &x);
   scanf("%d", &y);
   printf("Please choose desired operation from above menu. \n ");
   fflush(stdin);
   scanf("%c", &select);
   }

  printf("You have terminated the program.\n");
  return 0;
}
    /* Function Definitions */
	int addint (int x, int y)
	{
	 return x + y;	  
	}

	int subint (int x, int y)
	{
	  return x - y;
	}

	int multint (int x, int y)
	{ 
	  return x * y;
	}

	int divideint (int x, int y, int z)
	{   
		if (y != 0)
		{	     
		return x/y;
        return z=x%y;
		}
	}

	int powerint (int x, int y)
	{
		if (y==0)
		 return 1;
		else 
		 return (x *  powerint(x , y-1));	
	}
	
	int gcdint (int x,int y)
	{

        if (y!=0)
         return (gcdint(y, x%y));
        else
         return x;
}

	int factorial (int x, int y)
	{ 
          if (x == 0)
            return 1;
           else 
		  if (x >0)
			return x * factorial(x-1);
          if (y == 0)
            return 1;
           else 
		   if (y>0)
			  return y * factorial(y-1);
        }