Question

When I have

char anything[20];
cout << sizeof anything;

it prints 20.

However

string anymore;
cout << sizeof anymore; // it prints 4
getline(cin, anymore); // let's suppose I type more than one hundred characters
cout << sizeof anymore; // it still prints 4 !

I would like to understand how c++ manages this. Thanks

Answer 1

sizeof is a compile-time construct. It has nothing to do with runtime, but rather gives a fixed result based on the type passed to it (or the type of the value passed to it). So char[20] is 20 bytes, but a string might be 4 or 8 bytes or whatever depending on the implementation. The sizeof isn’t telling you how much storage the string allocated dynamically to hold its contents.