What value is stored in an array whose some element are not assigned?

Question

If i create an array as:

int number[10];
for(i=0;i<7,i+=1)
{
    cin>>number[i];
}

Then what will be the values stored in number[j], where j=8,9. And if some value is stored why and how are such values stored??

Answer 1

The answer depends on what storage duration the array has.

If it has the static storage duration when all its elements are zero initialized when the array is declared.

int number[10];

If the array has the automatic storage duration that is declared in a function without having the specifier static or extern when all its elements have indeterminate values.

Answer 2

They are uninitialized, meaning there could be any number stored in it, and you shouldn't rely on their value for anything.

Some compilers/systems might write zeros or certain patterns into it when running in debug mode, but you should never rely on that.

Answer 3

The values for number[8] and number[9] will be so called "garbage" value, which means it can be any number that is currently present in that location.

However if you initialize the array with partial initialization:

int number[10] = {1, 2, 3, 4, 5, 6, 7, 8};

Then the last 2 elements will be 0.

Answer 4

Modern software loaders clear the bits of a process' memory before turning it over to them. In that case, the values would be zero.

However, if you are cross-compiling, you cannot assume that the foreign loader will zero the bits. Always assign a value to a variable before using it (even if you're not cross-compiling).