Why doesn't my program crash when I write past the end of an array?

Question

Why does the code below work without any crash @ runtime ?

And also the size is completely dependent on machine/platform/compiler!!. I can even give upto 200 in a 64

Answer 1

By using an array type, which C++ has inherited from C, you are implicitly asking not to have a range check.

If you try this instead

void main(int argc, char* argv[])
{     
    std::vector arr(3);

    arr.at(4) = 99;
} 

you will get an exception thrown.

So C++ offers both a checked and an unchecked interface. It is up to you to select the one you want to use.