Unhandled exception at 0x0F828F0E (ucrtbased.dll) in Hello World.exe: 0xC0000005: Access violation writing location 0x00000002

Question

I am new in C++ and I've started to learn last night

I need help with the following error:

Unhandled exception at 0x0F828F0E (ucrtbased.dll) in Hello World.exe: 0xC0000005: Access violation writing location 0x00000002.

My code so far:

#include <iostream>
#include <conio.h>
#include <stdio.h>

using namespace std;

int main() {

    cout << "CUMPARATURI" << endl;

    int mere = 3 + 1;
    int banane = 16 / 4;

    cout << endl;
    cout << "Avem " << mere << " mere" << endl;
    cout << "Avem " << banane << " banane" << endl;

    int a = 16, b = 18;

    cout << endl;
    cout << "Valoarea lui a este " << a << endl;
    cout << "Dati o valoarea noua lui a : "; cin >> a;
    cout << "Noua valoarea a lui a este : " << a << endl;

    cout << endl;
    cout << "Acesta este primul rand \nAcesta este al 2-lea \nAcesta este al 3-lea";
    cout << endl;

    printf("\nAceasta este valoarea lui a: %d ", a);
    printf("\nLocatia lui a este %d \nDa-i valoare noua lui a : ", &a);
    scanf_s("%d", a);
    printf("Noua valoare a lui a este : %d",a);

    _getche();
    return 0;
};

Answer 1

If you take a look at the scanf_s documentation, you'll see that the variables you want to read data into are written after a &. The & takes the address of the variable, in fact scanf_s needs to know where to write the result in memory.

So, you should fix your code like this:

// Note '&a' instead of 'a'
scanf_s("%d", &a);

That said, in C++ you may want to consider std::cin for reading data into variables, e.g.:

int a{};
std::cin >> a;

Note that in this case there's no need to use the & (address-of) operator.