What is this output & why ?

Question

I wrote a code in which I declared an array & assigned no value to any index of the array & printed out the values from array , I got confusing output, pattern observed was that even index got non-zero number & odd index got 0 always . Why is this so ?
https://code.sololearn.com/cPwJUBx51o3b/?ref=app

Answer 1

You probably had small 64-bit numbers stored there, so every other 32-bits (the size of int) are zeros

Answer 2

Your array wasn't initialized so it contains garbage values. Please read these previous discussions regarding array and variable initialization:

See explanation from ~ swim ~ here:
https://www.sololearn.com/Discuss/1128723/?ref=app

See explanation from Dennis, and ~ swim ~ here:
https://www.sololearn.com/Discuss/1744856/?ref=app

You can simply change the array declaration to `int a[7] {};` this way the array will be initialized with default int type value (zero).

Answer 3

it is a wild value, the last value stored in the memory address you ordered, use this function to clear it

#include <iostream>
using namespace std;

void clear_arr(int *array, unsigned sum_elmt) {
for (unsigned i = 0; i < sum_elmt; ++ i)
array[i] = 0;
}

int main() {
int arr[7];

clear_arr(arr, 7);
cout<<arr[0]<<endl<<arr[1]<<endl<<arr[2]<<endl<<arr[3]<<endl<<arr[4]<<endl<<arr[5]<<endl<<arr[6];

return 0;
}