Variable has value without being assigned C++

Question

#include <iostream>
#include <string>


using namespace std;

int count_number_place(int number)
  {

    int number_placement;

    while (number >= 1)
     {
       number_placement++;
       cout << number_placement <<endl;
       number/=10;
     }

    return  number_placement;
  }



int main(int argc, const char * argv[]) 
  {
    // insert code here...

    int user_input_number;

    cout << "Please enter your number here" << endl;
    cin >> user_input_number;
    cout << "User input number is "<< user_input_number <<endl;
    cout << "The numbers of digits in the input number is :" << count_number_place(user_input_number) << endl;

    return 0;
  }

I'm trying to create a small program that calculates the number of digits of a given number.
Whenever I type in numbers like 200 the expected results is 3. Instead I got 7963. When I put a breakpoint at the line number_placement I got a default value of 7961 which is weird because that value wasn't assigned anywhere in the code.

Can you please explain why I get that result?

Answer 1

Just change your function to

int count_number_place(int number)
  {

    int number_placement = 0;         // assign 0

    while (number >= 1)
      {
        number_placement++;
        cout << number_placement <<endl;
        number/=10;
      }

    return  number_placement;
  }

That is, change

int number_placement;

to

int number_placement = 0; 

If you try to access uninitialized variables, you will get garbage values because it is undefined behavior. The compiler will just give it some garbage values.

This link might be useful

What happens to a declared, uninitialized variable in C? Does it have a value?