Does setting some fields of an array, set the others to zero?

Question

int main()
{
    int b[2][3]={{1,2},{3,4,5}};
    cout << b[0][2] << endl;
}

And the result in both visual and g++ is 0! Why? I thought it must be another number! For example, when we define int a[5] then we say cout << a[3]; without setting a[3], it will be something like, 0123984283 which means the last value of this cell in the RAM.

But here, What's the reason of 0?

score 5 · Accepted Answer · edited May 23 '17 at 11:49

5

If it is Partial Initialization, yes rest of the elements are guaranteed to be 0.

Here is a good read for Standerdese Fans and ones with eye for detail:

C and C++ : Partial initialization of automatic structure

edited May 23 '17 at 11:49

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answered Jun 17 '12 at 09:41

Alok Save

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What do you mean by Partial Initialization? – Milad R Jun 17 '12 at 09:42
@MiladR: Please read the linked answer, it explains in detail, why and how. – Alok Save Jun 17 '12 at 09:44
*Partial initialization* is not a term of C++, it is the term that someone used to ask a question. The term (for what is referred in the link as partial/full initialization) is **aggregate initialization**, and there is no specific term for *aggregate initialization* where not all of the fields are mentioned in the initializer list. – David Rodríguez - dribeas Jun 17 '12 at 12:20

score 1 · Answer 2 · edited May 23 '17 at 12:21

1

This answer has a more complete explanation with references to the documentation:

https://stackoverflow.com/a/629063/475523

edited May 23 '17 at 12:21

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answered Jun 17 '12 at 09:44

src

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Does setting some fields of an array, set the others to zero?

2 Answers2