Check out example codes for "how to make a calculator in c++". It will help you in understanding the concepts better.

Code Example 1

// ONLY 29 LINES OF CODE IN TOTAL
// For better calculator scroll down on this post
#include <iostream>
using namespace std;
int main() {
	cout << "Please enter the first number: ";
	double n1 = 0;
	cin >> n1;
	cout << "Please enter an operator (+, -, *, /): ";
	char op = '0';
	cin >> op;
	cout << "Please enter a second number: ";
	double n2 = 0;
	cin >> n2;
	double answer = 0;
	switch (op) {
	case '+': 
		answer = n1 + n2;
		break;
	case '-':
		answer = n1 - n2;
		break;
	case '*': 
		answer = n1 * n2;
		break;
	case '/': 
		answer = n1 / n2;
		break;
	}
	cout << "Thanks for using my calculator your answer is: " << answer;
  
  // this is the better calculator:
  
  #include <iostream>
#include <Windows.h>
using namespace std;
int main() {
	char jim = 'j';
	do {
		
		cout << "Please enter the first number: ";
		double n1 = 0;
		cin >> n1;
		cout << "Please enter an operator (+, -, *, /): ";
		char op = '0';
		cin >> op;
		cout << "Please enter a second number: ";
		double n2 = 0;
		cin >> n2;
		double answer = 0;
		switch (op) {
		case '+':
			answer = n1 + n2;
			break;
		case '-':
			answer = n1 - n2;
			break;
		case '*':
			answer = n1 * n2;
			break;
		case '/':
			answer = n1 / n2;
			break;
		}
		cout << "Thanks for using my calculator your answer is: " << answer << " do you want to run the program again? (y or n) ";
		cin >> jim;

	} while (jim = 'y' && jim != 'n');
	if (jim = 'n') {
		cout << "Thanks for using my calculator here is sum epic music";
		Beep(329, 300);
		Beep(493, 300);
		Beep(698, 300);
		Beep(659, 600);

		Beep(783, 300);
		Beep(698, 300);
		Beep(659, 600);

		Beep(329, 100);
		Beep(493, 300);
		Beep(698, 300);
		Beep(659, 600);

		Beep(392, 250);
		Beep(440, 200);
		Beep(587, 300);

		Beep(349, 250);
		Beep(587, 500);

		Beep(329, 300);
		Beep(493, 300);
		Beep(698, 300);
		Beep(659, 600);

		Beep(783, 300);
		Beep(698, 300);
		Beep(659, 600);

		Beep(329, 100);
		Beep(493, 300);
		Beep(698, 300);
		Beep(659, 600);

		Beep(392, 250);
		Beep(440, 200);
		Beep(587, 300);

		Beep(349, 250);
		Beep(587, 400);
	}
	return 0;
}

Code Example 2

// This is for beginners

#include <iostream>

using namespace std;

void greetings() {
    cout << "welcome to the calculator made in c++ :D\n";
}

void instructions() {
    cout << "Here is the operators you can use + - / *\n";
}

int main()
{
    greetings();
    instructions();
    int num1, num2;
    char op;
    int result;
    char again = 'Y';

    while (again == 'y' || again == 'Y') {



        cout << "\nEnter your first digit: ";
        cin >> num1;

        cout << "\nEnter your operator digit: ";
        cin >> op;

        cout << "\nEnter your second digit: ";
        cin >> num2;

        if (op == '+') {
            result = num1 + num2;
        }
        else if (op == '-') {
            result = num1 - num2;
        }
        else if (op == '*') {
            result = num1 * num2;
        }
        else if (op == '/') {
            result = num1 / num2;
        }
        else {
            cout << "Invalid operator";
        }

        cout << "= " << result;
        cout << "\nDo you want to restart the calculator? (Y or N)";
        cin >> again;
    }

    system("pause>0");

    return 0;
}

Code Example 3

#include<iostream>
using namespace std;
int calculator(int num1,int num2,int num3);
int main()
{
    //int num1,num2,num3,choice;
    int a,b,c,choice;
    cout<<"enter the first number"<<endl;
    cin>>a;
    cout<<"enter the second number"<<endl;
    cin>>b;
    cout<<"************************"<<endl;
    cout<<"****Make your choice****"<<endl;
    cout<<"1.Addition"<<endl;
    cout<<"2.Subtraction"<<endl;
    cout<<"3.Multiplication"<<endl;
    cout<<"4.Division"<<endl;
    cout<<"************************"<<endl;

    choice=calculator(a,b,c);
    return 0;
}
int calculator(int num1,int num2,int num3)
{

    int choice;
    cin>>choice;
    switch(choice)
    {

        case 1: cout<<"you have selected Addition"<<endl;
                num3=num1+num2;
                cout<<"Addition of two numbers is "<<num3<<endl;
                break;

        case 2: cout<<"you have selected Subtraction"<<endl;
                num3=num1-num2;
                cout<<"Subtraction of two numbers is "<<num3<<endl;
                break;

        case 3: cout<<"you have selected Multiplication"<<endl;
                num3=num1*num2;
                cout<<"Multiplication of two numbers is "<<num3<<endl;
                break;

        case 4: cout<<"You have selected Division"<<endl;
                num3=num1/num2;
                cout<<"Division of two numbers is "<<num3<<endl;
                break;

        default: cout<<"You have entered wrong choice"<<endl;
                    break;
    }
}

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