How to write a simple calculator program in C using if else?

Creating a simple calculator program in C using if-else statements is a great way to practice your programming skills. Below is a step-by-step guide along with the complete code for a basic calculator that can perform addition, subtraction, multiplication, and division.

Step-by-Step Guide

1. Include Necessary Headers: Start by including the standard input-output header file.
2. Declare Variables: You'll need variables to store the two numbers, the operator, and the result.
3. Get User Input: Prompt the user to enter two numbers and an operator.
4. Use if-else Statements: Based on the operator entered, use if-else statements to perform the corresponding arithmetic operation.
5. Display the Result: Print the result of the operation.
6. Handle Division by Zero: Ensure that the program checks for division by zero to avoid errors.

Complete Code

#include <stdio.h>

int main() {

    float num1, num2, result;

    char operator;

    // Get user input

    printf("Enter first number: ");

    scanf("%f", &num1);

    printf("Enter an operator (+, -, *, /): ");

    scanf(" %c", &operator); // Note the space before %c to consume any leftover whitespace

    printf("Enter second number: ");

    scanf("%f", &num2);

    // Perform calculation based on the operator

    if (operator == '+') {

        result = num1 + num2;

        printf("%.2f + %.2f = %.2f\n", num1, num2, result);

    } else if (operator == '-') {

        result = num1 - num2;

        printf("%.2f - %.2f = %.2f\n", num1, num2, result);

    } else if (operator == '*') {

        result = num1 * num2;

        printf("%.2f * %.2f = %.2f\n", num1, num2, result);

    } else if (operator == '/') {

        if (num2 != 0) {

            result = num1 / num2;

            printf("%.2f / %.2f = %.2f\n", num1, num2, result);

        } else {

            printf("Error! Division by zero.\n");

        }

    } else {

        printf("Invalid operator! Please use +, -, *, or /.\n");

    }

    return 0;

}

Explanation of the Code

1. Input Handling:

   • The program prompts the user to enter two numbers and an operator.
   • The scanf function is used to read the input values.

2. Calculation Logic:

   • The program checks the operator using if-else statements.
   • Depending on the operator, it performs the corresponding arithmetic operation.
   • For division, it checks if the second number is zero to prevent division by zero.

3. Output:

   • The result of the operation is printed to the console.
   • If the operator is invalid, an error message is displayed.

How to Compile and Run

1. Save the code in a file named calculator.c.
2. Open a terminal and navigate to the directory where the file is saved.
3. Compile the program using the following command:

gcc calculator.c -o calculator

Run the program:

./calculator

You can now enter numbers and operators to perform calculations! This simple calculator program is a great starting point for learning C programming and can be expanded with more features as you become more comfortable with the language.