Beginner C/C++ Exercises

Simple Calculator

A calculator combines a selected operation with branching and arithmetic.

What is Simple Calculator?

A calculator combines a selected operation with branching and arithmetic.

Apply an arithmetic operator to two numbers.

Important points

Compile with warnings enabled and fix every warning.
Know the lifetime and type of every value.
Validate input and keep array bounds explicit.

C and C++ code examples

Run code →

main.c

#include <stdio.h>
int main(void) {
    int left = 12, right = 4, result = 0; char operation = '*';
    // Select the calculation from the operator.
    switch (operation) { case '+': result = left + right; break; case '-': result = left - right; break; case '*': result = left * right; break; case '/': result = left / right; }
    printf("%d %c %d = %d\n", left, operation, right, result);
}

Expected output

12 * 4 = 48

C++

Run code →

main.cpp

#include <iostream>
int main() {
    int left = 12, right = 4, result = 0; char operation = '*';
    // Select the calculation from the operator.
    switch (operation) { case '+': result = left + right; break; case '-': result = left - right; break; case '*': result = left * right; break; case '/': result = left / right; }
    std::cout << left << ' ' << operation << ' ' << right << " = " << result << '\n';
}

Expected output

12 * 4 = 48

C and C++ comparison

The switch dispatches one character to the corresponding operation and keeps each case explicit.

C exposes small procedural APIs and makes representation details explicit.

C++

C++ retains the low-level model while adding safer library types and abstractions.

Practice exercises

Run both versions, then modify them to observe the different language guarantees.

Add invalid and boundary-value inputs.
Compile with -Wall -Wextra -Wpedantic.
Move reusable declarations into a header and implementation file.