Mine

/***********************************************
** Remy's Circle Equation Calculation Program **
************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#include <ctype.h>

#define PI 3.14

float a;
float c;

void prompt(void);
float area(void);
float circ(void);

void main()
{
	prompt();
}

float area(void)
{
	char rad[20];
	float r;
	float x;
 
	gets(rad);
	r=atoi(rad);
	x=PI*(r*r);

	return(x);
}	

float circ(void)
{
	char rad[20];
	float r;
	float x;

	gets(rad);
	r=atoi(rad);
	x=2*PI*r;

	return(x);
}

void prompt(void)
{
	printf("Press A for area, C for circumference, and Q to quit.\n");
	c=toupper(getch());

	if (c=='A')
	{
		printf("You chose area.\n");
		printf("Enter the radius:");	
   
		a=area();
		printf("The area of the circle is %f.\n",a);
	
		prompt();
	}
	
	else if (c=='C')
	{
		printf("You chose circumference.\n");
		printf("Enter the radius:");
	
		c=circ();
		printf("The circumference of the circle is %f.\n",c);
		
		prompt();
	}

	else if (c=='Q')
	{
		printf("Hit any key to close the program.\n");
		printf("Good bye!\n");
		
		getch();
	}

	else
	{
		printf("Invalid choice.\n");
		
		prompt();
	}
}