Integer在VSCommunity2019，windows10中未初始化

Question

I am making a calculator in c++ and I have everyting done except factorial which has one issue: my int number is "uninitialized" this is a console application on vscommunity2019 on windows10 if that helps. Everything works perfect except factorial,when I test it theonly error is the int number.

#include <iostream>
using namespace std;
int main()

{
float n1;
char op;
float n2;
int co;
int i;
int fact = 1;
int number;
calculations: std::cout << "Enter n1!";
    std::cin >> n1;
    std::cout << "\nEnter operator! Here are your choices: + - * / !";
    std::cin >> op;
    std::cout << "\nEnter n2!";
    std::cin >> n2;
    switch (op)
    {
    case '+':
        std::cout << n1 + n2;
        break;
case '-':
    std::cout << n1 - n2;
    break;

case '*':
    std::cout << n1 * n2;
    break;

case '/':
    std::cout << n1 / n2;
    break;
case '!':
    for (i = 1; i <= number; i++) {
        fact = fact * i;
    }
    std::cout << number;
    break;
default:
    std::cout << "Error! operator is not correct";
    break;
}
std::cout << "\nWant to continue?Y(type 1)/N(type 0)";
std::cin >> co;
if (co == 1) {

    goto calculations;
}
return 0;


}

Answer 1

Well, number is uninitialized.

int main()
{
int number; //uninitialized local variable
[...] //no usage of number
case '!':
    for (i = 1; i <= number; i++) { //first usage of number, before initializing it!
        fact = fact * i;
    }
    std::cout << number;
    break;
[...]
}

Luckily you get a compilation error and can fix it (thanks MSVC.), For gcc (when trying in compile explorer, it compiles. but I assume there will be a runtime error).

Solution? Probably replace number with n1 in the loop, and output fact .