Need help understanding the program solution for a book exercise

The exercise ask to make a calculator program to perform computations in a separate function for each type of computation.

Here is what my solution looks like and it works perfectly fine.

Code:

---


#include <iostream>

using namespace std;

// prototypes
int add(int x, int y);
int sub(int x, int y);
int mult(int x, int y);
int quo(int x, int y);


int main()
{
  int userChoice;
  int num1, num2;

  do {
    cout << "Which operation would you like to perform: \n";
    cout << "1. Add\n";
    cout << "2. Subtract\n";
    cout << "3. Multiply\n";
    cout << "4. Divide \n";
    cout << "5. Exit menu\n";
    cin >> userChoice;

    switch (userChoice) {
    case 1:
      cout << "Choose the first number you would like to add: \n";
      cin >> num1;
      cout << "Choose the second number you would like to add: \n";
      cin >> num2;
      cout << "The sum of the numbers is: " << add(num1, num2) << '\n';
      break;
    case 2:
      cout << "Pick the first number you would like to subtract: \n";
      cin >> num1;
      cout << "Choose the second number you would like to subtract: \n";
      cin >> num2;
      cout << "The difrence between the two numbers is: " << sub(num1, num2) << '\n';
      break;
    case 3:
      cout << "Choose the first nummber you would like to multiply: " << '\n';
      cin >> num1;
      cout << "Choose the second nummber you would like to multiply: " << '\n';
      cin >> num2;
      cout << "The product of the two numbers is: " << mult(num1, num2) << '\n';
      break;
    case 4:
      cout << "Choose the first nummber you would like to divide: " << '\n';
      cin >> num1;
      cout << "Choose the second nummber you would like to divide: " << '\n';
      cin >> num2;
      cout << "The quotient of the two numbers is: " << quo(num1, num2) << '\n';
      break;
    default:
      cout << "Exiting program...cya! \n";
      break;
    }
  } while (userChoice != 5);// exits menu

  system("pause");
  return 0;
}

// returns sum
int add(int x, int y) {
  return x + y;
}

// returns the difference
int sub(int x, int y) {
  return x - y;
}

// returns the product
int mult(int x, int y) {
  return x * y;
}

// returns the quotient
int quo(int x, int y) {
  return x / y;
}

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The solution in the book looks like this:

Code:

---

#include <iostream>

int multiply(int x, int y)
{
    return x*y;
}

int divide(int x, int y)
{
    return x/y;
}

int add(int x, int y)
{
    return x+y;
}

int subtract(int x, int y)
{
    return x-y;
}


using namespace std;

int main()
{
    char op='c';
    int x, y;
   
    while(op!='e')
    {
        cout<<"What operation would you like to perform: add(+), subtract(-), divide(/), multiply(*), [e]xit?";cin>>op;
        switch(op)
        {
            case '+':
            cin>>x;
            cin>>y;
            cout<<x<<"+"<<y<<"="<<add(x,y)<<endl;
            break;

            case '-':
            cin>>x;
            cin>>y;
            cout<<x<<"-"<<y<<"="<<subtract(x,y)<<endl;
            break;
           
            case '/':
            cin>>x;
            cin>>y;
           
            cout<<x<<"/"<<y<<"="<<divide(x,y)<<endl;
            break;
            case '*':
            cin>>x;
            cin>>y;
            cout<<x<<"*"<<y<<"="<<multiply(x,y)<<endl;
            break;
           
            case 'e':
            return 0;
           
            default:
            cout<<"Sorry, try again"<<endl;
        }
    }
    return 0;
}

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What I want to know is why does the solution use

Code:

---

char op = 'c';

---

I ran the solution with

Code:

---

char op;

---

and it still worked perfectly fine. Why is that and why do they use 'c'?

So that
while(op!='e')
Doesn't compare with a random uninitialized value which might randomly be e.

Thanks for the clarification! I have one more question. Would you say the book solution is better than the solution I came up with? Is there anything I could have done to make my solution better? Sorry, if what I'm asking is a dumb question.

Perhaps you could add another function to replace the code you copy and pasted.

Void prompt ( int &x, int &y, string prompt)