Simple Calculator with Menu


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

/** 
 * Function declarations for calculator
 */
int getoption(void);
float calc(int option, int num1, int num2);
float add(int num1, int num2);
float sub(int num1, int num2);
float mult(int num1, int num2);
float divi(int num1, int num2);

int main()
{
    int option;
    int num1, num2;
    float result;
    option = getoption();
    printf("Please enter two integer numbers:");
    scanf("%d%d", &num1, &num2);
    result = calc(option, num1, num2);
    printf("In main result is: %4.2f\n", result);
    return 0;
}

int getoption(void)
{
    int option;
    /* Print welcome message */
    printf("WELCOME TO SIMPLE CALCULATOR\n");
    printf("----------------------------\n");
    printf("Enter [number 1] : Add\n");
    printf("Enter [number 2] : Subtract\n");
    printf("Enter [number 3] : Multiply\n");
    printf("Enter [number 4] : Divide\n");

    /* Input two numbers and operator from the user */
    scanf("%d", &option);
    return option;
}

float calc(int option, int num1, int num2)
{
    float result;

    switch(option)
    {
        case 1: 
            result = add(num1, num2);
            break;

        case 2: 
            result = sub(num1, num2);
            break;

        case 3: 
            result = mult(num1, num2);
            break;

        case 4: 
            if (num2 == 0.0)
            {
                printf("Error");
                exit(0);
            }
            else
            {
                result = divi(num1, num2);
                break;
            }
        default: 
            printf("Invalid operator");
    }

    /* Print the result */
    printf("Result = %4.2f", result);

    return result;
}

/**
 * Function to add two numbers
 */
float add(int num1, int num2)
{
    return num1 + num2;
}

/**
 * Function to subtract two numbers
 */
float sub(int num1, int num2)
{
    return num1 - num2;
}

/**
 * Function to multiply two numbers
 */
float mult(int num1, int num2)
{
    return num1 * num2;
}

/**
 * Function to divide two numbers
 */
float divi(int num1, int num2)
{
    return num1 / num2;
}