内部字符串/字符如何存储在int和float中

Question

I have MISTAKENLY found the scenario while executing the following block of code

#include <iostream>
using namespace std;
int main()
{
    int input1;
    float input2;

    cout << "Enter a real number :";
    cin >> input1;
    cout << "The int number is " << input1 << endl;

    cout << "Enter another number :";
    cin >> input2;
    cout << "The float number is " << input2 << endl;
}

The output for the above is

Enter a real number :a
The int number is -858993460
Enter another number :a
The float number is -1.07374e+08

Can anyone kindly explain how internally the above scenario is getting handled resulting in the above scenario ?

Note -

• Running the above in VS2015.

As i am newly experimenting with C++, please point me to any reference if i have missed in the process.

Answer 1

int input1;
float input2;

At this point, both input1 and input2 have undefined values since you didn't initialize them.

std::cin was expecting an integer to be entered but you entered 'a' , which made std::cin to fail . That failure persists such that no extraction operation can be performed with std::cin until the failbit is cleared.

After your failed input operations, input1 and input2 are still "undefined". Printing them lead to Undefined Behavior.

Answer 2

The extraction operator does not change the variables when the stream cannot be interpreted as a valid value of the appropriate type. Therefore you see uninitialized values for input1 and input2 . You can check the failbit on cin to see whether the extraction operator was successful.

For example:

    int input1;
    cout << "Enter a real number :";
    cin >> input1;
    if(cin.good())
    {
        cout << "The int number is " << input1 << endl;
    }
    else
    {
       cout << "The input was not a number." << endl;

       // skip to the end of the input
       cin.clear();
       cin.ignore(INT_MAX, '\n');
    }