Building a Simple Calculator with C

Gathering Input

The first step in building our calculator is to gather input from the user. We need to know what operation they want to perform and what two numbers they want to operate on. To do this, we’ll use the scanf function to read in the operator (+, -, *, /) and two operands.

char op;
double first, second;
scanf(" %c %lf %lf", &op, &first, &second);

The Switch Statement: The Heart of Our Calculator

The switch statement is where the magic happens. We’ll use it to determine which operation to perform based on the operator entered by the user. The syntax is simple:

switch (op) {
    case '+':
        // addition
        break;
    case '-':
        // subtraction
        break;
    case '*':
        // multiplication
        break;
    case '/':
        // division
        break;
    default:
        printf("Invalid operator\n");
        break;
}

Performing Calculations

Once we’re inside the correct case block, we can perform the calculation. For example, for multiplication, we’ll simply multiply the two operands together:

result = first * second;

To make our output look cleaner, we’ll limit the result to one decimal place using the %.1lf format specifier:

printf("Result: %.1lf\n", result);

Breaking Out

Finally, we’ll use the break statement to exit the switch block and prevent the program from falling through to the next case. Without break, our program would continue executing code until it reaches the end of the switch block or encounters another break statement.

The Final Result

When we run our program, we’ll see the result of the calculation displayed on the screen. With the switch statement, break, and continue, we’ve built a simple yet powerful calculator that can perform basic arithmetic operations.

#include <stdio.h>

int main() {
    char op;
    double first, second, result;
    scanf(" %c %lf %lf", &op, &first, &second);

    switch (op) {
        case '+':
            result = first + second;
            break;
        case '-':
            result = first - second;
            break;
        case '*':
            result = first * second;
            break;
        case '/':
            if (second!= 0) {
                result = first / second;
            } else {
                printf("Error: Division by zero\n");
                return 1;
            }
            break;
        default:
            printf("Invalid operator\n");
            return 1;
    }

    printf("Result: %.1lf\n", result);

    return 0;
}