feat: Add basic C++ calculator

Src/Simple_Calculator/Calculator.cpp

@@ -0,0 +1,21 @@
+#include "Calculator.h"
+using namespace std;
+
+double Calculator::add(double a, double b) const {
+    return a+b;
+}
+
+double Calculator::subtract(double a, double b) const {
+    return a-b;
+}
+
+double Calculator::multiply(double a, double b) const {
+    return a*b;
+}
+
+double Calculator::divide(double a, double b) const {
+    if (b==0.0) {
+        throw invalid_argument("Division by zero is undefined");
+    }
+    return a/b;
+}

Src/Simple_Calculator/Calculator.h

@@ -0,0 +1,17 @@
+#pragma once
+#include <stdexcept>
+
+class Calculator {
+public:
+    // Adds two numbers
+    double add(double a, double b) const;
+
+    // Subtracts b from a
+    double subtract(double a, double b) const;
+
+    // Multiplies two numbers
+    double multiply(double a, double b) const;
+
+    // Divides a by b; throws invalid_argument on division by zero
+    double divide(double a, double b) const;
+};

Src/Simple_Calculator/README.md

@@ -24,3 +24,26 @@ The program is designed using **Object-Oriented Programming (OOP)** principles,
   - Clear and readable code  
 
 ---
+
+## Build & Run
+
+Files added:
+- `Calculator.h` - Calculator class declaration
+- `Calculator.cpp` - Calculator class implementation
+- `main.cpp` - Interactive console program
+
+Build (requires g++ and C++17):
+
+```powershell
+g++ -std=c++17 -Wall -Wextra -O2 main.cpp Calculator.cpp -o calculator.exe
+```
+
+Run:
+
+```powershell
+.\calculator.exe
+```
+
+Usage:
+- Enter a number, an operator (+, -, *, /), and a second number. Type `q` at any prompt to quit.
+

Src/Simple_Calculator/main.cpp

@@ -0,0 +1,52 @@
+#include <iostream>
+#include <string>
+#include <stdexcept> 
+#include "Calculator.h"
+using namespace std; 
+
+int main() {
+    Calculator calc;
+    cout << "Simple C++ Calculator\n";
+
+    while (true) { 
+        double a, b;
+        char op;
+
+        cout << "\nEnter an operator (+ - * /) or type 'q' to quit: ";
+        if (!(cin >> op) || op == 'q') {
+            break; 
+        }
+
+        if (op != '+' && op != '-' && op != '*' && op != '/') {
+            cout << "Invalid operator. Please use +, -, *, or /. Try again.\n";
+            continue; 
+        }
+
+        cout << "Enter first number: ";
+        if (!(cin >> a)) {
+            cout << "Invalid number input. Quitting.\n";
+            break; 
+        }
+
+        cout << "Enter second number: ";
+        if (!(cin >> b)) {
+            cout << "Invalid number input. Quitting.\n";
+            break;
+        }
+
+        try {
+            double result = 0.0;
+            switch (op) {
+                case '+': result = calc.add(a, b); break;
+                case '-': result = calc.subtract(a, b); break;
+                case '*': result = calc.multiply(a, b); break;
+                case '/': result = calc.divide(a, b); break;
+            }
+            cout << "Result: " << a << " " << op << " " << b << " = " << result << "\n";
+        } catch (const exception &ex) {
+            cout << "Error during calculation: " << ex.what() << "\n";
+        }
+    }
+    cout << "Thanks for using the Calculator!\n";
+    return 0;
+}