C Program to Make a Simple Calculator - Switch‑Case Operations

Simple Calculator Using Switch Statement

#include <stdio.h>

int main() {
    double num1, num2;
    char op;

    printf("Enter an operator (+, -, *, /, %c): ", '%');
    scanf(" %c", &op);

    printf("Enter two numbers: ");
    scanf("%lf %lf", &num1, &num2);

    switch (op) {
        case '+':
            printf("%.2lf + %.2lf = %.2lf\n", num1, num2, num1 + num2);
            break;
        case '-':
            printf("%.2lf - %.2lf = %.2lf\n", num1, num2, num1 - num2);
            break;
        case '*':
            printf("%.2lf * %.2lf = %.2lf\n", num1, num2, num1 * num2);
            break;
        case '/':
            if (num2 == 0) {
                printf("Error! Division by zero is not allowed.\n");
            } else {
                printf("%.2lf / %.2lf = %.2lf\n", num1, num2, num1 / num2);
            }
            break;
        case '%':
            // Modulus works on integers, cast the numbers
            printf("%d %% %d = %d\n", (int)num1, (int)num2, (int)num1 % (int)num2);
            break;
        default:
            printf("Error! Operator not supported.\n");
    }

    return 0;
}

Enter an operator (+, -, *, /, %): *
Enter two numbers: 7.5 4
7.5 * 4 = 30.00
        

Practice: Simple Calculator

This calculator asks the user to choose an operator and then enter two numbers. A switch statement performs the selected arithmetic operation. Note how division by zero is checked before attempting the calculation. Modulus requires integer operands, so casting is used when computing %.