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

To answer your question why it is "undetected": Most C compilers do not analyse at compile time what you are doing with pointers and with memory, and so nobody notices at compile time that you've written something dangerous. At runtime, there is also no controlled, managed environment that babysits your memory references, so nobody stops you from reading memory that you aren't entitled to. The memory happens to be allocated to you at that point (because its just part of the stack not far from your function), so the OS doesn't have a problem with that either.

If you want hand-holding while you access your memory, you need a managed environment like Java or CLI, where your entire program is run by another, managing program that looks out for those transgressions.