Variable length arrays (VLA) in C and C++

Question

Possible Duplicate:
Variably modified array at file scope

I have some concepts about the VLA and its behavior

Answer 1

I think the fundamental reason is a global variable has linkage, its size has to be known at compile time. If not, how could one link the program?

local variables have no linkage and the VLAs are allocated on the stack, which grows dynamically as the program runs.