Menu-Driven program using Switch-case in C

Prerequisite : Switch Case in C
Problem Statement: Write a menu-driven program using Switch case to calculate the following: 1. Area of circle 2. Area of square 3. Area of sphere Also use functions input() and output() to input and display respective values. 

C

// C program to illustrate
// Menu-Driven program
// using Switch-case

#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);
}

Output:

Press 1 to calculate area of circle
Press 2 to calculate area of square
Press 3 to calculate area of sphere
Enter your choice:
1
Enter radius:
5
Area of circle=78.5

Time Complexity: O(1)
Auxiliary Space: O(1)