area.c

#include <stdio.h>
int input();
void output(float);
int main()
{
	float result;
	int choice, num;
	printf("Press 1 to calculate area of circle\n");
	printf("Press 2 to calculate area of square\n");
	printf("Press 3 to calculate area of sphere\n");
	printf("Enter your choice:\n");
	choice = input();
	
	switch (choice) {
	case 1: {
		printf("Enter radius:\n");
		num = input();
		result = 3.14 * num * num;
		printf("Area of sphere=");
		output(result);
		break;
	}
	case 2: {
		printf("Enter side of square:\n");
		num = input();
		result = num * num;
		printf("Area of square=");
		output(result);
		break;
	}
	case 3: {
		printf("Enter radius:\n");
		num = input();
		result = 4 * (3.14 * num * num);
		printf("Area of sphere=");
		output(result);
		break;
	}
	default:
		printf("wrong Input\n");
	}
	return 0;
}
int input()
{
	int number;
	scanf("%d", &number);
	return (number);
}

void output(float number)
{
	printf("%f", number);
}